ORCID Profile
0000-0002-8303-7292
Current Organisations
University of Cambridge
,
Technische Universität München
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Publisher: Springer Science and Business Media LLC
Date: 15-04-2020
DOI: 10.1038/S41586-020-2184-1
Abstract: Halide perovskite materials have promising performance characteristics for low-cost optoelectronic applications. Photovoltaic devices fabricated from perovskite absorbers have reached power conversion efficiencies above 25 per cent in single-junction devices and 28 per cent in tandem devices
Publisher: American Chemical Society (ACS)
Date: 31-01-2023
Publisher: American Chemical Society (ACS)
Date: 09-08-2019
Publisher: American Physical Society (APS)
Date: 09-11-2009
Publisher: Springer Science and Business Media LLC
Date: 28-04-2023
DOI: 10.1038/S41467-023-38008-4
Abstract: Detecting low dose rates of X-rays is critical for making safer radiology instruments, but is limited by the absorber materials available. Here, we develop bismuth oxyiodide (BiOI) single crystals into effective X-ray detectors. BiOI features complex lattice dynamics, owing to the ionic character of the lattice and weak van der Waals interactions between layers. Through use of ultrafast spectroscopy, first-principles computations and detailed optical and structural characterisation, we show that photoexcited charge-carriers in BiOI couple to intralayer breathing phonon modes, forming large polarons, thus enabling longer drift lengths for the photoexcited carriers than would be expected if self-trapping occurred. This, combined with the low and stable dark currents and high linear X-ray attenuation coefficients, leads to strong detector performance. High sensitivities reaching 1.1 × 10 3 μC Gy air −1 cm −2 are achieved, and the lowest dose rate directly measured by the detectors was 22 nGy air s −1 . The photophysical principles discussed herein offer new design avenues for novel materials with heavy elements and low-dimensional electronic structures for (opto)electronic applications.
Publisher: American Chemical Society (ACS)
Date: 19-03-2014
DOI: 10.1021/JZ500209G
Abstract: Emerging from the field of dye-sensitized solar cells, organometal halide perovskite-based solar cells have recently attracted considerable attention. In these devices, the perovskite light absorbers can also be used as charge transporting materials, changing the requirements for efficient device architectures. The perovskite deposition can vary from merely sensitizing the TiO2 electron transporting scaffold as an endowment of small nanoparticles, to completely filling the pores where it acts as both light absorber and hole transporting material in one. By decreasing the TiO2 scaffold layer thickness, we change the solar cell architecture from perovskite-sensitized to completely perovskite-filled. We find that the latter case leads to improvements in device performance because higher electron densities can be sustained in the TiO2, improving electron transport rates and photovoltage. Importantly, the primary recombination pathway between the TiO2 and the hole transporting material is blocked by the perovskite itself. This understanding helps to rationalize the high voltages attainable on mesoporous TiO2-based perovskite solar cells.
Publisher: American Chemical Society (ACS)
Date: 18-11-2022
Publisher: American Physical Society (APS)
Date: 05-08-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3EE43822H
Publisher: Wiley
Date: 04-07-2021
Abstract: Hybrid‐perovskite‐based optoelectronic devices are demonstrating unprecedented growth in performance, and defect passivation approaches are highly promising routes to further improve properties. Here, the effect of the molecular ion BF 4 − , introduced via methylammonium tetrafluoroborate (MABF 4 ) in a surface treatment for MAPbI 3 perovskite, is reported. Optical spectroscopy characterization shows that the introduction of tetrafluoroborate leads to reduced non‐radiative charge‐carrier recombination with a reduction in first‐order recombination rate from 6.5 × 10 6 to 2.5 × 10 5 s −1 in BF 4 − ‐treated s les, and a consequent increase in photoluminescence quantum yield by an order of magnitude (from 0.5 to 10.4%). 19 F, 11 B, and 14 N solid‐state NMR is used to elucidate the atomic‐level mechanism of the BF 4 − additive‐induced improvements, revealing that the BF 4 − acts as a scavenger of excess MAI by forming MAI–MABF 4 cocrystals. This shifts the equilibrium of iodide concentration in the perovskite phase, thereby reducing the concentration of interstitial iodide defects that act as deep traps and non‐radiative recombination centers. These collective results allow us to elucidate the microscopic mechanism of action of BF 4 − .
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP05467D
Abstract: Controlled nucleation and growth by delaying the antisolvent dripping time leads to the formation of a textured perovskite thin film morphology with improved optoelectronic properties.
Publisher: American Chemical Society (ACS)
Date: 17-06-2021
Publisher: Research Square Platform LLC
Date: 15-09-2023
Publisher: Wiley
Date: 07-08-2019
Publisher: American Chemical Society (ACS)
Date: 05-12-2014
DOI: 10.1021/NN505860A
Abstract: Organic and hybrid organic-inorganic systems are promising candidates for low cost photovoltaics. Recently, perovskite-based systems have been attracting a large amount of research attention, where the highest performing devices employ a small molecule (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene) (Spiro-OMeTAD) hole transporter. Here, we demonstrate the production of single-walled carbon nanotube (SWNT)/single molecule nanostructures using a simple solution processing technique for effective and strong binding of Spiro-OMeTAD to in idual polymer-wrapped SWNTs. These small molecules bind very strongly, which causes both large mechanical strain of the nanotubes and also improves the separation of in idual SWNTs, thus improving the nanotube photoluminescence quantum efficiency by 1 order of magnitude compared to simple polymer-nanotube nanohybrids. Using absorption and photoluminescence measurements, we show that there is a dramatic variation in the electronic properties of the polymer-NT nanocomposites due to the band alignment formed with Spiro-OMeTAD. These self-assembled nanocomposites offer the potential for integration into high performance optoelectronic such as photovoltaic cells and light emission devices.
Publisher: American Chemical Society (ACS)
Date: 08-07-2015
DOI: 10.1021/ACS.NANOLETT.5B00678
Abstract: Organic-inorganic perovskites are highly promising solar cell materials with laboratory-based power conversion efficiencies already matching those of established thin film technologies. Their exceptional photovoltaic performance is in part attributed to the presence of efficient radiative recombination pathways, thereby opening up the possibility of efficient light-emitting devices. Here, we demonstrate optically pumped lified spontaneous emission (ASE) at 780 nm from a 50 nm-thick film of CH3NH3PbI3 perovskite that is sandwiched within a cavity composed of a thin-film (∼7 μm) cholesteric liquid crystal (CLC) reflector and a metal back-reflector. The threshold fluence for ASE in the perovskite film is reduced by at least two orders of magnitude in the presence of the CLC reflector, which results in a factor of two reduction in threshold fluence compared to previous reports. We consider this to be due to improved coupling of the oblique and out-of-plane modes that are reflected into the bulk in addition to any contributions from cavity modes. Furthermore, we also demonstrate enhanced ASE on flexible reflectors and discuss how improvements in the quality factor and reflectivity of the CLC layers could lead to single-mode lasing using CLC reflectors. Our work opens up the possibility of fabricating widely wavelength-tunable "mirror-less" single-mode lasers on flexible substrates, which could find use in applications such as flexible displays and friend or foe identification.
Publisher: American Chemical Society (ACS)
Date: 09-12-2014
DOI: 10.1021/NN505723H
Abstract: Organic-inorganic perovskites, such as CH3NH3PbX3 (X=I, Br, Cl), have emerged as attractive absorber materials for the fabrication of low cost high efficiency solar cells. Over the last 3 years, there has been an exceptional rise in power conversion efficiencies (PCEs), demonstrating the outstanding potential of these perovskite materials. However, in most device architectures, including the simplest thin-film planar structure, a current-voltage response displays an "anomalous hysteresis", whereby the power output of the cell varies with measurement time, direction and light exposure or bias history. Here we provide insight into the physical processes occurring at the interface between the n-type charge collection layer and the perovskite absorber. Through spectroscopic measurements, we find that electron transfer from the perovskite to the TiO2 in the standard planar junction cells is very slow. By modifying the n-type contact with a self-assembled fullerene monolayer, electron transfer is "switched on", and both the n-type and p-type heterojunctions with the perovskite are active in driving the photovoltaic operation. The fullerene-modified devices achieve up to 17.3% power conversion efficiency with significantly reduced hysteresis, and stabilized power output reaching 15.7% in the planar p-i-n heterojunction solar cells measured under simulated AM 1.5 sunlight.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7EE00685C
Abstract: The authors directly show that grain size and quality have a negligible impact on the excitonic characteristics of perovskite semiconductors.
Publisher: American Chemical Society (ACS)
Date: 08-12-2015
DOI: 10.1021/JACS.5B09085
Abstract: Despite rapid developments in both photovoltaic and light-emitting device performance, the understanding of the optoelectronic properties of hybrid lead halide perovskites is still incomplete. In particular, the polarizability of the material, the presence of molecular dipoles, and their influence on the dynamics of the photoexcitations remain an open issue to be clarified. Here, we investigate the effect of an applied external electric field on the photoexcited species of CH3NH3PbI3 thin films, both at room temperature and at low temperature, by monitoring the photoluminescence (PL) yield and PL decays. At room temperature we find evidence for electric-field-induced reduction of radiative bimolecular carrier recombination together with motion of charged defects that affects the nonradiative decay rate of the photoexcited species. At low temperature (190 K), we observe a field-induced enhancement of radiative free carrier recombination rates that lasts even after the removal of the field. We assign this to field-induced alignment of the molecular dipoles, which reduces the vibrational freedom of the lattice and the associated local screening and hence results in a stronger electron-hole interaction.
Publisher: AIP Publishing
Date: 07-09-2015
DOI: 10.1063/1.4930144
Abstract: Multi-band gap heterojunction solar cells fabricated from a blend of 1.2 eV and 1.4 eV PbS colloidal quantum dots (CQDs) show poor device performance due to non-radiative recombination. To overcome this, a CdS shell is epitaxially formed around the PbS core using cation exchange. From steady state and transient photoluminescence measurements, we understand the nature of charge transfer between these quantum dots. Photoluminescence decay lifetimes are much longer in the PbS/CdS core/shell blend compared to PbS only, explained by a reduction in non-radiative recombination resulting from CdS surface passivation. PbS/CdS heterojunction devices sustain a higher open-circuit voltage and lower reverse saturation current as compared to PbS-only devices, implying lower recombination rates. Further device performance enhancement is attained by modifying the composition profile of the CQD species in the absorbing layer resulting in a three dimensional quantum cascade structure.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4EE03224A
Abstract: Thorough measurements of the optical constants of CH 3 NH 3 PbI 3 are used to determine the limiting parasitic losses in solar cells revealing up to 100% IQE and excellent performance at oblique incidence.
Publisher: American Chemical Society (ACS)
Date: 20-06-2012
DOI: 10.1021/NN301133V
Abstract: We describe studies of new nanostructured materials consisting of carbon nanotubes wrapped in sequential coatings of two different semiconducting polymers, namely, poly(3-hexylthiophene) (P3HT) and poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT). Using absorption spectroscopy and steady-state and ultrafast photoluminescence measurements, we demonstrate the role of the different layer structures in controlling energy levels and charge transfer in both solution and film s les. By varying the simple solution processing steps, we can control the ordering and proportions of the wrapping polymers in the solid state. The resulting novel coaxial structures open up a variety of new applications for nanotube blends and are particularly promising for implementation into organic photovoltaic devices. The carbon nanotube template can also be used to optimize both the electronic properties and morphology of polymer composites in a much more controlled fashion than achieved previously, offering a route to producing a new generation of polymer nanostructures.
Publisher: American Chemical Society (ACS)
Date: 03-04-2020
DOI: 10.1021/JACS.0C00647
Publisher: IOP Publishing
Date: 14-05-2021
Abstract: The use of pulsed mode scanning electron microscopy cathodoluminescence (CL) for both hyperspectral mapping and time-resolved measurements is found to be useful for the study of hybrid perovskite films, a class of ionic semiconductors that have been shown to be beam sensitive. A range of acquisition parameters is analysed, including beam current and beam mode (either continuous or pulsed operation), and their effect on the CL emission is discussed. Under optimized acquisition conditions, using a pulsed electron beam, the heterogeneity of the emission properties of hybrid perovskite films can be resolved via the acquisition of CL hyperspectral maps. These optimized parameters also enable the acquisition of time-resolved CL of polycrystalline films, showing significantly shorter lived charge carriers dynamics compared to the photoluminescence analogue, hinting at additional electron beam-specimen interactions to be further investigated. This work represents a promising step to investigate hybrid perovskite semiconductors at the nanoscale with CL.
Publisher: American Physical Society (APS)
Date: 11-09-2014
Publisher: American Chemical Society (ACS)
Date: 07-2014
DOI: 10.1021/NN502115K
Abstract: Solution-processed organometal trihalide perovskite solar cells are attracting increasing interest, leading to high performances over 15% in thin film architectures. Here, we probe the presence of sub gap states in both solid and mesosuperstructured perovskite films and determine that they strongly influence the photoconductivity response and splitting of the quasi-Fermi levels in films and solar cells. We find that while the planar perovskite films are superior to the mesosuperstructured films in terms of charge carrier mobility (in excess of 20 cm(2) V(-1) s(-1)) and emissivity, the planar heterojunction solar cells are limited in photovoltage by the presence of sub gap states and low intrinsic doping densities.
Publisher: American Chemical Society (ACS)
Date: 10-06-2015
Abstract: We have employed soft and hard X-ray photoelectron spectroscopies to study the depth-dependent chemical composition of mixed-halide perovskite thin films used in high-performance solar cells. We detect substantial amounts of metallic lead in the perovskite films, which correlate with significant density of states above the valence band maximum. The metallic lead content is higher in the bulk of the perovskite films than at the surface. Using an optimized postanneal process in air, we can reduce the metallic lead content in the perovskite film. This process reduces the amount of metallic lead and a corresponding increase in the photoluminescence quantum efficiency of the perovskite films can be observed. This correlation indicates that metallic lead impurities are likely a key defect whose concentration can be controlled by simple annealing procedures in order to increase the performance for perovskite solar cells.
Publisher: Springer Science and Business Media LLC
Date: 22-11-2019
Publisher: American Chemical Society (ACS)
Date: 21-09-2023
Publisher: American Chemical Society (ACS)
Date: 22-07-2020
Publisher: Springer Science and Business Media LLC
Date: 18-10-2021
DOI: 10.1038/S41467-021-26340-6
Abstract: There is a growing interest in obtaining high quality monolayer transition metal disulfides for optoelectronic applications. Surface treatments using a range of chemicals have proven effective to improve the photoluminescence yield of these materials. However, the underlying mechanism for the photoluminescence enhancement is not clear, which prevents a rational design of passivation strategies. Here, a simple and effective approach to significantly enhance the photoluminescence is demonstrated by using a family of cation donors, which we show to be much more effective than commonly used p-dopants. We develop a detailed mechanistic picture for the action of these cation donors and demonstrate that one of them, bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI), enhances the photoluminescence of both MoS 2 and WS 2 to a level double that of the currently best performing super-acid trifluoromethanesulfonimide (H-TFSI) treatment. In addition, the ionic salts used in our treatments are compatible with greener solvents and are easier to handle than super-acids, providing the possibility of performing treatments during device fabrication. This work sets up rational selection rules for ionic chemicals to passivate transition metal disulfides and increases their potential in practical optoelectronic applications.
Publisher: Wiley
Date: 09-05-2019
DOI: 10.1002/MPR.1782
Publisher: Springer Science and Business Media LLC
Date: 15-06-2015
DOI: 10.1038/NPHYS3357
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-05-2015
Abstract: Great strides have been made in improving the efficiency of organic-inorganic perovskite solar cells. Further improvements are likely to depend on understanding the role of film morphology on charge-carrier dynamics. de Quilettes et al. correlated confocal fluorescence microscopy images with those from scanning electron microscopy to spatially resolve the photoluminescence and carrier decay dynamics from films of organic-inorganic perovskites. Carrier lifetimes varied widely even between grains, and chemical treatments could improve lifetimes Science , this issue p. 683
Publisher: Springer Science and Business Media LLC
Date: 15-03-2023
Publisher: AIP Publishing
Date: 28-07-2014
DOI: 10.1063/1.4889845
Abstract: We have fabricated CH3NH3PbI3−xClx perovskite thin films crystallized in situ on substrates of different natures (e.g., porosity, wettability) and investigated their photoluminescence properties. We observe that the crystallization time and thin film structure are strongly influenced by the chemical nature and porosity of the substrate. Moreover, we find that the mesoporous scaffold can tune the emissive properties of the semiconducting compound both in terms of spectral region and dynamics. In particular, perovskite crystallites grown in the nanometre size porous scaffold present a shorter-living and blue-shifted emission with respect to the perovskite crystals which are free to grow without any constraints.
Publisher: American Chemical Society (ACS)
Date: 25-06-2013
DOI: 10.1021/NL401044Q
Abstract: A plethora of solution-processed materials have been developed for solar cell applications. Hybrid solar cells based on light absorbing semiconducting polymers infiltrated into mesoporous TiO2 are an interesting concept, but generating charge at the polymer-metal oxide heterojunction is challenging. Metal-organic perovskite absorbers have recently shown remarkable efficiencies but currently lack the range of color tunability of organics. Here, we have combined a fullerene self-assembled monolayer (C60SAM) functionalized mesoporous titania, a perovskite absorber (CH3NH3PbI3-xClx), and a light absorbing polymer hole-conductor, P3HT, to realize a 6.7% efficient hybrid solar cell. We find that photoexcitations in both the perovskite and the polymer undergo very efficient electron transfer to the C60SAM. The C60SAM acts as an electron acceptor but inhibits further electron transfer into the TiO2 mesostructure due to energy level misalignment and poor electronic coupling. Thermalized electrons from the C60SAM are then transported through the perovskite phase. This strategy allows a reduction of energy loss, while still employing a "mesoporous electron acceptor", representing an exciting and versatile route forward for hybrid photovoltaics incorporating light-absorbing polymers. Finally, we show that we can use the C60SAM functionalization of mesoporous TiO2 to achieve an 11.7% perovskite-sensitized solar cell using Spiro-OMeTAD as a transparent hole transporter.
Publisher: AIP Publishing
Date: 28-05-2014
DOI: 10.1063/1.4879895
Abstract: We demonstrate ultrafast modulation of terahertz radiation by unaligned optically pumped single-walled carbon nanotubes. Photoexcitation by an ultrafast optical pump pulse induces transient terahertz absorption in nanowires aligned parallel to the optical pump. By controlling the polarisation of the optical pump, we show that terahertz polarisation and modulation can be tuned, allowing sub-picosecond modulation of terahertz radiation. Such speeds suggest potential for semiconductor nanowire devices in terahertz communication technologies.
Publisher: American Chemical Society (ACS)
Date: 17-07-2018
Publisher: Wiley
Date: 03-03-2021
Abstract: Halide perovskites have attracted considerable attention in next‐generation solid‐state lighting and displays owing to their outstanding optoelectronic properties. Over the past few years, perovskite light‐emitting diodes (LEDs) have achieved high external quantum efficiencies of % with active layers showing photoluminescence quantum efficiencies close to unity. This paper reviews the historical breakthroughs and recent advancements in perovskite LEDs with near‐infrared, red, green, and blue emission colors. Critical challenges, including device stability and material toxicity, are discussed. Finally, an outlook on white emission and lasing applications based on perovskite materials is presented.
Publisher: American Chemical Society (ACS)
Date: 22-05-2018
Abstract: Perovskite-based optoelectronic devices have been rapidly developing in the past 5 years. Since the first report, the external quantum efficiency (EQE) of perovskite light-emitting diodes (PeLEDs) has increased rapidly through the control of morphology and structure from 0.1% to more than 11%. Here, we report the use of various conjugated polyelectrolytes (CPEs) as the hole injection layer in PeLEDs. In particular, we find that poly[2,6-(4,4-bis-potassium butanylsulfonate)-4 H-cyclopenta-[2,1- b ,4- b']-dithiophene)] (PCPDT-K) transfers holes effectively, blocks electron transport from the perovskite to the underlying ITO layer, and reduces luminescence quenching at the perovskite/PCPDT-K interface. Our optimized PeLEDs with PCPDT-K show enhanced EQE by a factor of approximately 4 compared to control PeLEDs with PEDOT:PSS, reaching EQE values of 5.66%, and exhibit improved device stability.
Publisher: American Chemical Society (ACS)
Date: 16-08-1970
Publisher: Springer Science and Business Media LLC
Date: 30-03-2022
Publisher: American Chemical Society (ACS)
Date: 28-02-2011
DOI: 10.1021/NN103588H
Abstract: We report on the noncovalent binding of conjugated porphyrin oligomers to small diameter single-walled carbon nanotubes (SWNTs) and highlight two remarkable observations. First, the binding of the oligomers to SWNTs is so strong that it induces mechanical strain on the nanotubes in solution. The magnitudes of the strains are comparable to those found in solid-state studies. Comparable strains are not observed in any other SWNT-supramolecular complexes. Second, large decreases in polymer band gap with increasing length of the oligomer lead to the formation of a type-II heterojunction between long chain oligomers and small-diameter nanotubes. This is demonstrated by the observation of enhanced red-shifts for the nanotube interband transitions. These complexes offer considerable promise for photovoltaic devices.
Publisher: American Chemical Society (ACS)
Date: 09-12-2009
DOI: 10.1021/JF902365R
Abstract: Grape thaumatin-like (TL) proteins and chitinases play roles in plant-pathogen interactions and can cause protein haze in white wine unless removed prior to bottling. A two-step method is described that highly purified hundreds of milligrams of TL proteins and chitinases from two juices by strong cation exchange (SCX) and hydrophobic interaction chromatography (HIC). The method was fast and separated isoforms of TL proteins and chitinases from within the same juice, in most cases to >97% purity. The isolated proteins were identified by peptide nanoLC-MS/MS and crystallized using a high-throughput screening method. Crystals from three protein fractions produced high-resolution X-ray crystallography data.
Publisher: Wiley
Date: 08-07-2015
Publisher: Springer Science and Business Media LLC
Date: 09-07-2019
Publisher: American Physical Society (APS)
Date: 20-06-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6EE03201J
Abstract: Mixed-metal compositional screening identifies Co 2+ as capable of partial B-site substitution in CH 3 NH 3 PbI 3 , which supplies new dimensions of material tunability.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9NR09622A
Abstract: This work investigates the formation of APbBr 3 structures (A = CH 3 NH 3 + (MA), Cs + ) in silicon and oxidized silicon nanotubes (SiNTs) with varying inner diameter, as well as the role of the interface in perovskite spectroscopic properties.
Publisher: Wiley
Date: 31-03-2022
Abstract: The interaction of high‐energy electrons and X‐ray photons with beam‐sensitive semiconductors such as halide perovskites is essential for the characterization and understanding of these optoelectronic materials. Using nanoprobe diffraction techniques, which can investigate physical properties on the nanoscale, studies of the interaction of electron and X‐ray radiation with state‐of‐the‐art (FA 0.79 MA 0.16 Cs 0.05 )Pb(I 0.83 Br 0.17 ) 3 hybrid halide perovskite films (FA, formamidinium MA, methylammonium) are performed, tracking the changes in the local crystal structure as a function of fluence using scanning electron diffraction and synchrotron nano X‐ray diffraction techniques. Perovskite grains are identified, from which additional reflections, corresponding to PbBr 2 , appear as a crystalline degradation phase after fluences of 200 e − Å − 2 . These changes are concomitant with the formation of small PbI 2 crystallites at the adjacent high‐angle grain boundaries, with the formation of pinholes, and with a phase transition from tetragonal to cubic. A similar degradation pathway is caused by photon irradiation in nano‐X‐ray diffraction, suggesting common underlying mechanisms. This approach explores the radiation limits of these materials and provides a description of the degradation pathways on the nanoscale. Addressing high‐angle grain boundaries will be critical for the further improvement of halide polycrystalline film stability, especially for applications vulnerable to high‐energy radiation such as space photovoltaics.
Publisher: Springer Science and Business Media LLC
Date: 17-11-2022
DOI: 10.1038/S41563-022-01395-Y
Abstract: Fast diffusion of charge carriers is crucial for efficient charge collection in perovskite solar cells. While lateral transient photoluminescence microscopies have been popularly used to characterize charge diffusion in perovskites, there exists a discrepancy between low diffusion coefficients measured and near-unity charge collection efficiencies achieved in practical solar cells. Here, we reveal hidden microscopic dynamics in halide perovskites through four-dimensional (directions x, y and z and time t) tracking of charge carriers by characterizing out-of-plane diffusion of charge carriers. By combining this approach with confocal microscopy, we discover a strong local heterogeneity of vertical charge diffusivities in a three-dimensional perovskite film, arising from the difference between intragrain and intergrain diffusion. We visualize that most charge carriers are efficiently transported through the direct intragrain pathways or via indirect detours through nearby areas with fast diffusion. The observed anisotropy and heterogeneity of charge carrier diffusion in perovskites rationalize their high performance as shown in real devices. Our work also foresees that further control of polycrystal growth will enable solar cells with micrometres-thick perovskites to achieve both long optical path length and efficient charge collection simultaneously.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9TA11854C
Abstract: We report morphological control with phenyl-C60-butyric acid methyl ester (PCBM) molecular aggregation for perovskite–PCBM bulk heterostructure (Pe–PCBM BHS) solar cells.
Publisher: Wiley
Date: 07-08-2022
Abstract: Mixed-halide mixed-cation hybrid perovskites are among the most promising perovskite compositions for application in a variety of optoelectronic devices due to their high performance, low cost, and bandgap-tuning capabilities. Instability pathways such as those driven by ionic migration, however, continue to hinder their further progress. Here, an operando variable-pitch synchrotron grazing-incidence wide-angle X-ray scattering technique is used to track the surface and bulk structural changes in mixed-halide mixed-cation perovskite solar cells under continuous load and illumination. By monitoring the evolution of the material structure, it is demonstrated that halide remixing along the electric field and illumination direction during operation hinders phase segregation and limits device instability. Correlating the evolution with directionality- and depth-dependent analyses, it is proposed that this halide remixing is induced by an electrostrictive effect acting along the substrate out-of-plane direction. However, this stabilizing effect is overwhelmed by competing halide demixing processes in devices exposed to humid air or with poorer starting performance. The findings shed new light on understanding halide de- and re-mixing competitions and their impact on device longevity. These operando techniques allow real-time tracking of the structural evolution in full optoelectronic devices and unveil otherwise inaccessible insights into rapid structural evolution under external stress conditions.
Publisher: American Chemical Society (ACS)
Date: 16-05-2022
Publisher: American Chemical Society (ACS)
Date: 11-11-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2EE02698H
Abstract: Photoemission spectroscopy reveals halogen cleavage from bulky cation organics and the formation process of 2D-like perovskites on the parent perovskite as well as their impact on band alignment and device performance.
Publisher: Wiley
Date: 16-11-2020
Publisher: American Chemical Society (ACS)
Date: 19-08-2013
DOI: 10.1021/NL4024287
Abstract: Recently, inorganic and hybrid light absorbers such as quantum dots and organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured organometal halide perovskite solar cells incorporating core-shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facile tuning of exciton binding energies in perovskite semiconductors.
Publisher: American Chemical Society (ACS)
Date: 14-12-2022
Publisher: American Chemical Society (ACS)
Date: 04-09-2019
Publisher: Wiley
Date: 02-12-2015
Abstract: A general strategy for the in-plane structuring of organic-inorganic perovskite films is presented. The method is used to fabricate an industrially relevant distributed feedback (DFB) cavity, which is a critical step toward all-electrially pumped injection laser diodes. This approach opens the prospects of perovskite materials for much improved optical control in LEDs, solar cells, and also toward applications as optical devices.
Publisher: American Chemical Society (ACS)
Date: 27-11-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8EE00928G
Abstract: Perovskite solar cells and light-emission devices are yet to achieve their full potential owing in part to spatially heterogeneous non-radiative loss pathways that are both on, and buried beneath, the surfaces of films and crystals.
Publisher: Wiley
Date: 06-02-2015
Publisher: American Chemical Society (ACS)
Date: 24-07-2015
DOI: 10.1021/ACS.JPCLETT.5B01361
Abstract: Efficient solar cells have been obtained using thin films of solution-processed organic-inorganic perovskites. However, there remains limited knowledge about the relationship between preparation route and optoelectronic properties. We use complementary time-resolved microwave conductivity (TRMC) and photoluminescence (PL) measurements to investigate the charge carrier dynamics in thin planar films of CH3NH3PbI(3-x)Cl(x), CH3NH3PbI3, and their meso-structured analogues. High mobilities close to 30 cm(2)/(V s) and microsecond-long lifetimes are found in thin films of CH3NH3PbI(3-x)Cl(x), compared to lifetimes of only a few hundred nanoseconds in CH3NH3PbI3 and meso-structured perovskites. We describe our TRMC and PL experiments with a global kinetic model, using one set of kinetic parameters characteristic for each s le. We find that the trap density is less than 5 × 10(14) cm(-3) in CH3NH3PbI(3-x)Cl(x), 6 × 10(16) cm(-3) in the CH3NH3PbI3 thin film and ca. 10(15) cm(-3) in both meso-structured perovskites. Furthermore, our results imply that band-to-band recombination is enhanced by the presence of dark carriers resulting from unintentional doping of the perovskites. Finally, our general approach to determine concentrations of trap states and dark carriers is also highly relevant to other semiconductor materials.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2EE01343F
Abstract: Local manufacturing of perovskite solar cells is feasible in many low- and lower-middle income countries and would boost the economy by providing jobs, adding value to local resources and providing a reliable clean energy source.
Publisher: American Chemical Society (ACS)
Date: 13-05-2021
Publisher: Springer Science and Business Media LLC
Date: 05-2015
Abstract: Metal-halide perovskites are crystalline materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technology to commercialization.
Publisher: Wiley
Date: 03-02-2022
DOI: 10.1002/JEMT.24069
Abstract: Cross-sectional transmission electron microscopy has been widely used to investigate organic-inorganic hybrid halide perovskite-based optoelectronic devices. Electron-transparent specimens (lamellae) used in such studies are often prepared using focused ion beam (FIB) milling. However, the gallium ions used in FIB milling may severely degrade the structure and composition of halide perovskites in the lamellae, potentially invalidating studies performed on them. In this work, the close relationship between perovskite structure and luminescence is exploited to examine the structural quality of perovskite solar cell lamellae prepared by FIB milling. Through hyperspectral cathodoluminescence (CL) mapping, the perovskite layer was found to remain optically active with a slightly blue-shifted luminescence. This finding indicates that the perovskite structure is largely preserved upon the lamella fabrication process although some surface amorphisation occurred. Further changes in CL due to electron beam irradiation were also recorded, confirming that electron dose management is essential in electron microscopy studies of carefully prepared halide perovskite-based device lamellae. RESEARCH HIGHLIGHTS: Cathodoluminescence is used to study the emission of focused ion beam milled perovskite solar cell lamellae. The perovskite remained optically active with a slightly blue-shifted luminescence, indicating that the perovskite structure is mostly preserved.
Publisher: American Chemical Society (ACS)
Date: 09-09-2019
DOI: 10.1021/ACS.CHEMREV.9B00169
Abstract: The success of halide perovskites in a host of optoelectronic applications is often attributed to their long photoexcited carrier lifetimes, which has led to charge-carrier recombination processes being described as unique compared to other semiconductors. Here, we integrate recent literature findings to provide a critical assessment of the factors we believe are most likely controlling recombination in the most widely studied halide perovskite systems. We focus on four mechanisms that have been proposed to affect measured charge carrier recombination lifetimes, namely: (1) recombination via trap states, (2) polaron formation, (3) the indirect nature of the bandgap (e.g., Rashba effect), and (4) photon recycling. We scrutinize the evidence for each case and the implications of each process on carrier recombination dynamics. Although they have attracted considerable speculation, we conclude that multiple trapping or hopping in shallow trap states, and the possible indirect nature of the bandgap (e.g., Rashba effect), seem to be less likely given the combined evidence, at least in high-quality s les most relevant to solar cells and light-emitting diodes. On the other hand, photon recycling appears to play a clear role in increasing apparent lifetime for s les with high photoluminescence quantum yields. We conclude that polaron dynamics are intriguing and deserving of further study. We highlight potential interdependencies of these processes and suggest future experiments to better decouple their relative contributions. A more complete understanding of the recombination processes could allow us to rationally tailor the properties of these fascinating semiconductors and will aid the discovery of other materials exhibiting similarly exceptional optoelectronic properties.
Publisher: American Chemical Society (ACS)
Date: 22-01-2021
Publisher: Springer Science and Business Media LLC
Date: 19-10-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1SC03775G
Abstract: Mixed valence Sn doping of Cs 3 Bi 2 Br 9 leads to broad visible light absorption.
Publisher: American Chemical Society (ACS)
Date: 22-09-2023
DOI: 10.1021/JACS.3C05974
Publisher: American Chemical Society (ACS)
Date: 17-06-2014
DOI: 10.1021/CM501595U
Publisher: Wiley
Date: 30-05-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1EE02055B
Abstract: Hybrid halide perovskites are found to contain multiple types of nanoscale defects that play varied roles in charge trapping – from highly detrimental to relatively benign.
Publisher: Research Square Platform LLC
Date: 21-06-2022
DOI: 10.21203/RS.3.RS-1767937/V1
Abstract: While perovskite photovoltaic (PV) devices are on the verge of their commercialization, promising methods to recycle or remanufacture fully-encapsulated perovskite solar cells (PSCs) and modules are still missing. Through detailed life-cycle assessment shown in this work, we identify that the majority of the greenhouse gas emissions can be reduced by re-using the glass substrate and parts of the PV cells. Based on these analytical findings, we develop a novel thermally-assisted mechanochemical approach to remove the encapsulants, the electrode and the perovskite absorber, allowing to re-use most of the device constituents for remanufacturing PSCs, which recovered nearly 90% of their initial performance. This remanufacturing strategy allows to save up to 33% of the module’s global warming potential. Finally, we demonstrate that the CO 2 -footprint of these remanufactured devices can become less than 30g/kWh, which is the value for state-of-the-art c-Si PV modules and can even reach 15g/kWh assuming a similar lifetime
Publisher: American Chemical Society (ACS)
Date: 29-01-2019
Publisher: Springer Science and Business Media LLC
Date: 24-05-2016
DOI: 10.1038/NCOMMS11683
Abstract: Organic–inorganic perovskites such as CH 3 NH 3 PbI 3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH 3 NH 3 PbI 3 films under illumination. We demonstrate that the photo-induced ‘brightening’ of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.
Publisher: Wiley
Date: 12-02-2020
Publisher: American Chemical Society (ACS)
Date: 27-06-2022
DOI: 10.1021/JACS.2C02631
Publisher: American Chemical Society (ACS)
Date: 14-06-2021
Publisher: American Chemical Society (ACS)
Date: 29-08-2014
DOI: 10.1021/NL502016Q
Abstract: Semiconducting carbon nanotubes (CNTs) provide an exceptional platform for studying one-dimensional excitons (bound electron-hole pairs), but the role of defects and quenching centers in controlling emission remains controversial. Here we show that, by wrapping the CNT in a polymer sheath and cooling to 4.2 K, ultranarrow photoluminescence (PL) emission line widths below 80 μeV can be seen from in idual solution processed CNTs. Hyperspectral imaging of the tubes identifies local emission sites and shows that some previously dark quenching segments can be brightened by the application of high magnetic fields, and their effect on exciton transport and dynamics can be studied. Using focused high intensity laser irradiation, we introduce a single defect into an in idual nanotube which reduces its quantum efficiency by the creation of a shallow bound exciton state with enhanced electron-hole exchange interaction. The emission intensity of the nanotube is then reactivated by the application of the high magnetic field.
Publisher: American Chemical Society (ACS)
Date: 02-08-2017
Publisher: Hindawi Limited
Date: 30-05-2018
DOI: 10.1002/DA.22778
Publisher: Springer Science and Business Media LLC
Date: 30-04-2020
Publisher: American Chemical Society (ACS)
Date: 17-04-2019
Publisher: American Chemical Society (ACS)
Date: 07-05-2014
DOI: 10.1021/NL500627X
Abstract: Organic-inorganic halide perovskites, such as CH3NH3PbX3 (X = I(-), Br(-), Cl(-)), are attracting growing interest to prepare low-cost solar cells that are capable of converting sunlight to electricity at the highest efficiencies. Despite negligible effort on enhancing materials' purity or passivation of surfaces, high efficiencies have already been achieved. Here, we show that trap states at the perovskite surface generate charge accumulation and consequent recombination losses in working solar cells. We identify that undercoordinated iodine ions within the perovskite structure are responsible and make use of supramolecular halogen bond complexation to successfully passivate these sites. Following this strategy, we demonstrate solar cells with maximum power conversion efficiency of 15.7% and stable power output over 15% under constant 0.81 V forward bias in simulated full sunlight. The surface passivation introduces an important direction for future progress in perovskite solar cells.
Publisher: Wiley
Date: 16-09-2016
Abstract: Carbon nanotubes have a variety of remarkable electronic and mechanical properties that, in principle, lend them to promising optoelectronic applications. However, the field has been plagued by heterogeneity in the distributions of synthesized tubes and uncontrolled bundling, both of which have prevented nanotubes from reaching their full potential. Here, a variety of recently demonstrated solution-processing avenues is presented, which may combat these challenges through manipulation of nanoscale structures. Recent advances in polymer-wrapping of single-walled carbon nanotubes (SWNTs) are shown, along with how the resulting nanostructures can selectively disperse tubes while also exploiting the favorable properties of the polymer, such as light-harvesting ability. New methods to controllably form nanoengineered SWNT networks with controlled nanotube placement are discussed. These nanoengineered networks decrease bundling, lower the percolation threshold, and enable a strong enhancement in charge conductivity compared to random networks, making them potentially attractive for optoelectronic applications. Finally, SWNT applications, to date, in organic and perovskite photovoltaics are reviewed, and insights as to how the aforementioned recent advancements can lead to improved device performance provided.
Publisher: Springer Science and Business Media LLC
Date: 2011
DOI: 10.1557/OPL.2011.230
Abstract: We report the observation of an ultrafast (~ 430 fs) charge transfer process at the interface between a single-walled carbon nanotube (SWNT) wrapped by a semi-conducting polymer, poly(3-hexylthiophene) (P3HT), creating free polarons on both materials. The addition of excess P3HT as a surrounding network allows these free polarons to be long-lived at room temperature. Our results suggest that SWNT-P3HT blends incorporating only 1% fractions of SWNTs can achieve a charge separation efficiency comparable to a conventional 60:40 P3HT-fullerene blend, provided small-diameter tubes are embedded in an excess P3HT matrix.
Publisher: Springer Science and Business Media LLC
Date: 12-06-2023
Publisher: Springer Science and Business Media LLC
Date: 30-01-2015
DOI: 10.1038/NCOMMS7142
Abstract: To date, there have been a plethora of reports on different means to fabricate organic-inorganic metal halide perovskite thin films however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.
Publisher: American Chemical Society (ACS)
Date: 02-04-2014
DOI: 10.1021/JZ5005285
Abstract: The study of the photophysical properties of organic-metallic lead halide perovskites, which demonstrate excellent photovoltaic performance in devices with electron- and hole-accepting layers, helps to understand their charge photogeneration and recombination mechanism and unravels their potential for other optoelectronic applications. We report surprisingly high photoluminescence (PL) quantum efficiencies, up to 70%, in these solution-processed crystalline films. We find that photoexcitation in the pristine CH3NH3PbI3-xClx perovskite results in free charge carrier formation within 1 ps and that these free charge carriers undergo bimolecular recombination on time scales of 10s to 100s of ns. To exemplify the high luminescence yield of the CH3NH3PbI3-xClx perovskite, we construct and demonstrate the operation of an optically pumped vertical cavity laser comprising a layer of perovskite between a dielectric mirror and evaporated gold top mirrors. These long carrier lifetimes together with exceptionally high luminescence yield are unprecedented in such simply prepared inorganic semiconductors, and we note that these properties are ideally suited for photovoltaic diode operation.
Publisher: American Chemical Society (ACS)
Date: 28-05-2021
Publisher: Wiley
Date: 07-03-2018
Abstract: Metal halide perovskites are exceptional candidates for inexpensive yet high-performing optoelectronic devices. Nevertheless, polycrystalline perovskite films are still limited by nonradiative losses due to charge carrier trap states that can be affected by illumination. Here, in situ microphotoluminescence measurements are used to elucidate the impact of light-soaking in idual methylammonium lead iodide grains in high-quality polycrystalline films while immersing them with different atmospheric environments. It is shown that emission from each grain depends sensitively on both the environment and the nature of the specific grain, i.e., whether it shows good (bright grain) or poor (dark grain) luminescence properties. It is found that the dark grains show substantial rises in emission, while the bright grain emission is steady when illuminated in the presence of oxygen and/or water molecules. The results are explained using density functional theory calculations, which reveal strong adsorption energies of the molecules to the perovskite surfaces. It is also found that oxygen molecules bind particularly strongly to surface iodide vacancies which, in the presence of photoexcited electrons, lead to efficient passivation of the carrier trap states that arise from these vacancies. The work reveals a unique insight into the nature of nonradiative decay and the impact of atmospheric passivation on the microscale properties of perovskite films.
Publisher: Springer Science and Business Media LLC
Date: 24-08-2022
DOI: 10.1038/S41467-022-32669-3
Abstract: I-V-VI 2 ternary chalcogenides are gaining attention as earth-abundant, nontoxic, and air-stable absorbers for photovoltaic applications. However, the semiconductors explored thus far have slowly-rising absorption onsets, and their charge-carrier transport is not well understood yet. Herein, we investigate cation-disordered NaBiS 2 nanocrystals, which have a steep absorption onset, with absorption coefficients reaching 5 cm −1 just above its pseudo-direct bandgap of 1.4 eV. Surprisingly, we also observe an ultrafast (picosecond-time scale) photoconductivity decay and long-lived charge-carrier population persisting for over one microsecond in NaBiS 2 nanocrystals. These unusual features arise because of the localised, non-bonding S p character of the upper valence band, which leads to a high density of electronic states at the band edges, ultrafast localisation of spatially-separated electrons and holes, as well as the slow decay of trapped holes. This work reveals the critical role of cation disorder in these systems on both absorption characteristics and charge-carrier kinetics.
Publisher: American Chemical Society (ACS)
Date: 06-06-2017
Publisher: Springer Science and Business Media LLC
Date: 18-10-2021
Publisher: American Chemical Society (ACS)
Date: 04-05-2022
Publisher: Springer Science and Business Media LLC
Date: 26-01-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4OB02507E
Abstract: We report the synthesis of four new cationic push–pull membrane probes based on a thiophene core and evaluate their photobiological properties.
Publisher: American Chemical Society (ACS)
Date: 20-09-2013
DOI: 10.1021/JP405734F
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TC01595H
Abstract: The origins of the remarkable performance of halide perovskite scintillators are presented, along with solutions to the challenges facing the field, followed by a discussion of applications that will benefit from the unique properties of these materials.
Publisher: Wiley
Date: 30-05-2014
Publisher: Wiley
Date: 12-10-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4EE01076K
Abstract: Perovskite solar cells based on abundant low cost materials promise to compete on performance with mainstream PV. Here we demonstrate lead-free perovskite solar cells, removing a potential barrier to widespread deployment.
Publisher: Wiley
Date: 22-02-2013
Abstract: A scalable method to coat monochiral (7,5) semiconducting single-walled carbon nanotubes with a monolayer coating of a range of technologically useful polymers such as poly(3-hexylthiophene) (P3HT) and poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) is presented. Optical spectroscopy and atomic force microscopy measurements show that the semiconducting tube purity (>99%) obtained from the selective wrapping of nanotubes by polymers such as poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) can be transferred to these other nanotube-polymer combinations by polymer exchange.
Publisher: Wiley
Date: 17-12-2019
Abstract: There has been a meteoric rise in the commercial potential of lead halide perovskite optoelectronic devices since photovoltaic cells and light‐emitting diodes based on these materials were first demonstrated. One key challenge common to each of these optoelectronic devices is the need to suppress nonradiative recombination, a process that limits the maximum achievable efficiency in photovoltaic cells and light‐emitting diodes. In this Progress Report, recent studies that seek to minimize this loss pathway in perovskites through a photobrightening treatment, whereby the luminescence efficiency is enhanced through a light illumination passivation process are examined. The sensitivity of this effect to various experimental considerations is examined, including atmosphere, photon energy, photon dose, and also the role of perovskite composition and morphology under certain conditions there can even be photodarkening effects. Consideration of these factors is critical to resolve seemingly conflicting literature reports. Proposed mechanisms are scrutinized, revealing that there is now some consensus but further work is needed to identify the specific defects being passivated and elucidate universal mechanisms. Finally, the prospects for these treatments to minimize halide migration and push the properties of polycrystalline films towards those of their single‐crystal counterparts are discussed.
Publisher: Wiley
Date: 10-07-2020
Publisher: American Chemical Society (ACS)
Date: 12-10-2020
Publisher: Wiley
Date: 25-08-2021
Abstract: Riding on the coat tails of rapid developments in single‐junction halide perovskite solar cells, all‐perovskite multijunction solar cells have recently garnered significant attention, with the highest power‐conversion efficiency already reaching 25.6%. Much of this progress has been fueled by the rapid rise in the photovoltaic performance of low‐bandgap halide perovskite absorbers, materials, which, to date, have only been achievable by the partial or complete substitution of lead with tin. However, much room still exists to develop a more critical understanding of key material properties in these low‐bandgap perovskites. Herein, the key optoelectronic properties of absorption, carrier generation, recombination, and transport in these tin‐containing perovskites are discussed, showing that intrinsic doping distinctively impacts many of these properties, thereby rendering this class of halide perovskites unique within the family. Current understanding of the mechanisms that degrade optoelectronic performance in these materials and the corresponding devices are also summarized. These collective results highlight an important interplay between doping, defects, and degradation that will need to be controlled. Finally, the current gaps in understanding of these low‐bandgap perovskites are outlined, thereby providing guidelines for further research, which will unlock their full potential for realizing a plethora of high‐performance optoelectronic devices.
Publisher: American Chemical Society (ACS)
Date: 19-11-2015
Publisher: American Chemical Society (ACS)
Date: 03-12-2019
Publisher: Springer Science and Business Media LLC
Date: 16-06-2015
Publisher: Wiley
Date: 03-09-2013
Abstract: Solid‐state dye‐sensitized solar cells rely on effective infiltration of a solid‐state hole‐transporting material into the pores of a nanoporous TiO 2 network to allow for dye regeneration and hole extraction. Using microsecond transient absorption spectroscopy and femtosecond photoluminescence upconversion spectroscopy, the hole‐transfer yield from the dye to the hole‐transporting material 2,2′,7,7′‐tetrakis( N,N ‐di‐p‐methoxyphenylamine)‐9,9'‐spirobifluorene (spiro‐OMeTAD) is shown to rise rapidly with higher pore‐filling fractions as the dye‐coated pore surface is increasingly covered with hole‐transporting material. Once a pore‐filling fraction of ≈30% is reached, further increases do not significantly change the hole‐transfer yield. Using simple models of infiltration of spiro‐OMeTAD into the TiO 2 porous network, it is shown that this pore‐filling fraction is less than the amount required to cover the dye surface with at least a single layer of hole‐transporting material, suggesting that charge diffusion through the dye monolayer network precedes transfer to the hole‐transporting material. Comparison of these results with device parameters shows that improvements of the power‐conversion efficiency beyond ≈30% pore filling are not caused by a higher hole‐transfer yield, but by a higher charge‐collection efficiency, which is found to occur in steps. The observed sharp onsets in photocurrent and power‐conversion efficiencies with increasing pore‐filling fraction correlate well with percolation theory, predicting the points of cohesive pathway formation in successive spiro‐OMeTAD layers adhered to the pore walls. From percolation theory it is predicted that, for standard mesoporous TiO 2 with 20 nm pore size, the photocurrent should show no further improvement beyond an ≈83% pore‐filling fraction.
Publisher: American Chemical Society (ACS)
Date: 12-11-2019
Publisher: American Chemical Society (ACS)
Date: 18-12-2014
DOI: 10.1021/JZ502367K
Abstract: Efficient, neutral-colored semitransparent solar cells are of commercial interest for incorporation into the windows and surfaces of buildings and automobiles. Here, we report on semitransparent perovskite solar cells that are both efficient and neutral-colored, even in full working devices. Using the microstructured architecture previously developed, we achieve higher efficiencies by replacing methylammonium lead iodide perovskite with formamidinium lead iodide. Current-voltage hysteresis is also much reduced. Furthermore, we apply a novel transparent cathode to the devices, enabling us to fabricate neutral-colored semitransparent full solar cells for the first time. Such devices demonstrate over 5% power conversion efficiency for average visible transparencies of almost 30%, retaining impressive color-neutrality. This makes these devices the best-performing single-junction neutral-colored semitransparent solar cells to date. These microstructured perovskite solar cells are shown to have a significant advantage over silicon solar cells in terms of performance at high incident angles of sunlight, making them ideal for building integration.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8EE02751J
Abstract: Halide perovskites are found to exhibit strain patterns over large areas, which influences the lifetimes of charge carriers.
Publisher: American Chemical Society (ACS)
Date: 25-10-2019
Publisher: Wiley
Date: 06-09-2018
Abstract: Light emission is a critical property that must be maximized and controlled to reach the performance limits in optoelectronic devices such as photovoltaic solar cells and light-emitting diodes. Halide perovskites are an exciting family of materials for these applications owing to uniquely promising attributes that favor strong luminescence in device structures. Herein, the current understanding of the physics of light emission in state-of-the-art metal-halide perovskite devices is presented. Photon generation and management, and how these can be further exploited in device structures, are discussed. Key processes involved in photoluminescence and electroluminescence in devices as well as recent efforts to reduce nonradiative losses in neat films and interfaces are discussed. Finally, pathways toward reaching device efficiency limits and how the unique properties of perovskites provide a tremendous opportunity to significantly disrupt both the power generation and lighting industries are outlined.
Publisher: American Chemical Society (ACS)
Date: 06-03-2015
DOI: 10.1021/NN506465N
Abstract: Recently, solution-processable organic-inorganic metal halide perovskites have come to the fore as a result of their high power-conversion efficiencies (PCE) in photovoltaics, exceeding 17%. To attain reproducibility in the performance, one of the critical factors is the processing conditions of the perovskite film, which directly influences the photophysical properties and hence the device performance. Here we study the effect of annealing parameters on the crystal structure of the perovskite films and correlate these changes with its photophysical properties. We find that the crystal formation is kinetically driven by the annealing atmosphere, time and temperature. Annealing in air produces an improved crystallinity and large grain domains as compared to nitrogen. Lower photoluminescence quantum efficiency (PLQE) and shorter photoluminescence (PL) lifetimes are observed for nitrogen annealed perovskite films as compared to the air-annealed counterparts. We note that the limiting nonradiative pathways (i.e., maximizing PLQE) is important for obtaining the highest device efficiency. This indicates a critical impact of the atmosphere upon crystallization and the ultimate device performance.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3RA03846G
Abstract: In this work, we fabricate & test MA-free co-evaporated perovskite solar cells that could potentially be fabricated in space. Pseudo- JV characteristics & electroluminescence hereby help to distinguish radiation damage from parasitic effects.
Publisher: Springer Science and Business Media LLC
Date: 22-11-2021
Publisher: American Chemical Society (ACS)
Date: 05-09-2019
Publisher: American Chemical Society (ACS)
Date: 03-09-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TC04406D
Abstract: Films of the two-dimensional Dion–Jacobson compound PDMAPbI 4 are studied through concerted multimodal microscopy. Hyperspectral Raman and PL imaging underline the complex impact of the microstructure, composition, and orientation on the photophysics.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0EE03839C
Abstract: A mixed-cation single-crystal lead-halide perovskite absorber layer was utilized to construct 22.8%-efficient solar cells with an expanded near infrared response that approaches the ideal bandgap range (1.1–1.4 eV) for single-junction solar cells.
Publisher: American Chemical Society (ACS)
Date: 21-08-2019
Publisher: American Chemical Society (ACS)
Date: 25-06-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5EE03435C
Abstract: The reduced effective mass ( μ ) and excitonic Rydberg ( R *) are measured by magneto-optics for new perovskite semiconductors.
Publisher: American Psychological Association (APA)
Date: 10-2018
DOI: 10.1037/ABN0000362
Publisher: American Chemical Society (ACS)
Date: 30-11-2022
Publisher: Wiley
Date: 11-11-2019
Abstract: Halide perovskites are emerging as valid alternatives to conventional photovoltaic active materials owing to their low cost and high device performances. This material family also shows exceptional tunability of properties by varying chemical components, crystal structure, and dimensionality, providing a unique set of building blocks for new structures. Here, highly stable self-assembled lead-tin perovskite heterostructures formed between low-bandgap 3D and higher-bandgap 2D components are demonstrated. A combination of surface-sensitive X-ray diffraction, spatially resolved photoluminescence, and electron microscopy measurements is used to reveal that microstructural heterojunctions form between high-bandgap 2D surface crystallites and lower-bandgap 3D domains. Furthermore, in situ X-ray diffraction measurements are used during film formation to show that an ammonium thiocyanate additive delays formation of the 3D component and thus provides a tunable lever to substantially increase the fraction of 2D surface crystallites. These novel heterostructures will find use in bottom cells for stable tandem photovoltaics with a surface 2D layer passivating the 3D material, or in energy-transfer devices requiring controlled energy flow from localized surface crystallites to the bulk.
Publisher: Wiley
Date: 06-09-2019
Abstract: Mixed-halide lead perovskites have attracted significant attention in the field of photovoltaics and other optoelectronic applications due to their promising bandgap tunability and device performance. Here, the changes in photoluminescence and photoconductance of solution-processed triple-cation mixed-halide (Cs
Publisher: American Chemical Society (ACS)
Date: 21-01-2022
Publisher: American Chemical Society (ACS)
Date: 25-08-2018
Publisher: American Chemical Society (ACS)
Date: 30-09-2019
Publisher: American Chemical Society (ACS)
Date: 08-08-2016
Abstract: Colloidal perovskite nanoplatelets are a promising class of semiconductor nanomaterials-exhibiting bright luminescence, tunable and spectrally narrow absorption and emission features, strongly confined excitonic states, and facile colloidal synthesis. Here, we demonstrate the high degree of spectral tunability achievable through variation of the cation, metal, and halide composition as well as nanoplatelet thickness. We synthesize nanoplatelets of the form L2[ABX3]n-1BX4, where L is an organic ligand (octylammonium, butylammonium), A is a monovalent metal or organic molecular cation (cesium, methylammonium, formamidinium), B is a alent metal cation (lead, tin), X is a halide anion (chloride, bromide, iodide), and n-1 is the number of unit cells in thickness. We show that variation of n, B, and X leads to large changes in the absorption and emission energy, while variation of the A cation leads to only subtle changes but can significantly impact the nanoplatelet stability and photoluminescence quantum yield (with values over 20%). Furthermore, mixed halide nanoplatelets exhibit continuous spectral tunability over a 1.5 eV spectral range, from 2.2 to 3.7 eV. The nanoplatelets have relatively large lateral dimensions (100 nm to 1 μm), which promote self-assembly into stacked superlattice structures-the periodicity of which can be adjusted based on the nanoplatelet surface ligand length. These results demonstrate the versatility of colloidal perovskite nanoplatelets as a material platform, with tunability extending from the deep-UV, across the visible, into the near-IR. In particular, the tin-containing nanoplatelets represent a significant addition to the small but increasingly important family of lead- and cadmium-free colloidal semiconductors.
Publisher: American Chemical Society (ACS)
Date: 28-09-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6EE01504B
Abstract: The photoinduced removal of trap states due to Frenkel defects is found to enhance the PLQE of perovskite thin films.
Publisher: American Chemical Society (ACS)
Date: 24-05-2023
Publisher: Wiley
Date: 28-07-2021
Abstract: Lead‐free Cs 2 AgBiBr 6 double perovskite is considered a promising alternative photovoltaic absorber to the widely used lead halide perovskite due to its easy processability, high stability, and reduced toxicity. Herein, for the first time spray processing for the deposition of Cs 2 AgBiBr 6 double perovskite thin films is reported. Microstructural (X‐ray diffraction, scanning electron microscopy) and optoelectronic (absorbance, photoluminescence, photocurrent density versus applied voltage curves, electrochemical impedance spectroscopy) properties of spray‐coated film are compared with the spin‐coated benchmark. Incorporation of the spray‐coated Cs 2 AgBiBr 6 double perovskite thin films in solar cells leads to a 2.3% photoconversion efficiency with high open‐circuit voltage of 1.09 V. This study highlights the suitability of ultrasonic spray deposition for the optimization of Cs 2 AgBiBr 6 solar cells in terms of light absorption properties and charge transfer at the Cs 2 AgBiBr 6 /hole transporting layer interface.
Publisher: Springer Science and Business Media LLC
Date: 11-11-2019
Publisher: American Chemical Society (ACS)
Date: 10-04-2014
DOI: 10.1021/JZ500113X
Abstract: Perovskite solar cells have rapidly risen to the forefront of emerging photovoltaic technologies, exhibiting rapidly rising efficiencies. This is likely to continue to rise, but in the development of these solar cells there are unusual characteristics that have arisen, specifically an anomalous hysteresis in the current-voltage curves. We identify this phenomenon and show some ex les of factors that make the hysteresis more or less extreme. We also demonstrate stabilized power output under working conditions and suggest that this is a useful parameter to present, alongside the current-voltage scan derived power conversion efficiency. We hypothesize three possible origins of the effect and discuss its implications on device efficiency and future research directions. Understanding and resolving the hysteresis is essential for further progress and is likely to lead to a further step improvement in performance.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7EE03013D
Abstract: Simultaneous GI-WAXS diffraction patterns and JV measurement of IBC solar cells during in situ anneal.
Publisher: Springer Science and Business Media LLC
Date: 08-04-2014
DOI: 10.1038/NCOMMS4586
Abstract: Excitonic solar cells, within which bound electron-hole pairs have a central role in energy harvesting, have represented a hot field of research over the last two decades due to the compelling prospect of low-cost solar energy. However, in such cells, exciton dissociation and charge collection occur with significant losses in energy, essentially due to poor charge screening. Organic-inorganic perovskites show promise for overcoming such limitations. Here, we use optical spectroscopy to estimate the exciton binding energy in the mixed-halide crystal to be in the range of 50 meV. We show that such a value is consistent with almost full ionization of the exciton population under photovoltaic cell operating conditions. However, increasing the total photoexcitation density, excitonic species become dominant, widening the perspective of this material for a host of optoelectronic applications.
Publisher: Wiley
Date: 18-01-2016
Abstract: Methylammonium lead halide (MAPbX3 ) perovskites exhibit exceptional carrier transport properties. But their commercial deployment as solar absorbers is currently limited by their intrinsic instability in the presence of humidity and their lead content. Guided by our theoretical predictions, we explored the potential of methylammonium bismuth iodide (MBI) as a solar absorber through detailed materials characterization. We synthesized phase-pure MBI by solution and vapor processing. In contrast to MAPbX3, MBI is air stable, forming a surface layer that does not increase the recombination rate. We found that MBI luminesces at room temperature, with the vapor-processed films exhibiting superior photoluminescence (PL) decay times that are promising for photovoltaic applications. The thermodynamic, electronic, and structural features of MBI that are amenable to these properties are also present in other hybrid ternary bismuth halide compounds. Through MBI, we demonstrate a lead-free and stable alternative to MAPbX3 that has a similar electronic structure and nanosecond lifetimes.
Publisher: American Chemical Society (ACS)
Date: 04-08-2016
DOI: 10.1021/JACS.6B06320
Abstract: Lead halide perovskites have over the past few years attracted considerable interest as photo absorbers in PV applications with record efficiencies now reaching 22%. It has recently been found that not only the composition but also the precise stoichiometry is important for the device performance. Recent reports have, for ex le, demonstrated small amount of PbI2 in the perovskite films to be beneficial for the overall performance of both the standard perovskite, CH3NH3PbI3, as well as for the mixed perovskites (CH3NH3)x(CH(NH2)2)(1-x)PbBryI(3-y). In this work a broad range of characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photo electron spectroscopy (PES), transient absorption spectroscopy (TAS), UV-vis, electroluminescence (EL), photoluminescence (PL), and confocal PL mapping have been used to further understand the importance of remnant PbI2 in perovskite solar cells. Our best devices were over 18% efficient, and had in line with previous results a small amount of excess PbI2. For the PbI2-deficient s les, the photocurrent dropped, which could be attributed to accumulation of organic species at the grain boundaries, low charge carrier mobility, and decreased electron injection into the TiO2. The PbI2-deficient compositions did, however, also have advantages. The record Voc was as high as 1.20 V and was found in PbI2-deficient s les. This was correlated with high crystal quality, longer charge carrier lifetimes, and high PL yields and was rationalized as a consequence of the dynamics of the perovskite formation. We further found the ion migration to be obstructed in the PbI2-deficient s les, which decreased the JV hysteresis and increased the photostability. PbI2-deficient synthesis conditions can thus be used to deposit perovskites with excellent crystal quality but with the downside of grain boundaries enriched in organic species, which act as a barrier toward current transport. Exploring ways to tune the synthesis conditions to give the high crystal quality obtained under PbI2-poor condition while maintaining the favorable grain boundary characteristics obtained under PbI2-rich conditions would thus be a strategy toward more efficiency devices.
Publisher: Wiley
Date: 31-03-2021
Abstract: Halide perovskites are a versatile class of semiconductors employed for high performance emerging optoelectronic devices, including flexoelectric systems, yet the influence of their ionic nature on their mechanical behavior is still to be understood. Here, a combination of atomic‐force, optical, and compositional X‐ray microscopy techniques is employed to shed light on the mechanical properties of halide perovskite films at the nanoscale. Mechanical domains within and between morphological grains, enclosed by mechanical boundaries of higher Young's Modulus (YM) than the bulk parent material, are revealed. These mechanical boundaries are associated with the presence of bromide‐rich clusters as visualized by nano‐X‐ray fluorescence mapping. Stiffer regions are specifically selectively modified upon light soaking the s le, resulting in an overall homogenization of the mechanical properties toward the bulk YM. This behavior is attributed to light‐induced ion migration processes that homogenize the local chemical distribution, which is accompanied by photobrightening of the photoluminescence within the same region. This work highlights critical links between mechanical, chemical, and optoelectronic characteristics in this family of perovskites, and demonstrates the potential of combinational imaging studies to understand and design halide perovskite films for emerging applications such as photoflexoelectricity.
Publisher: Springer Science and Business Media LLC
Date: 16-09-2021
Publisher: American Chemical Society (ACS)
Date: 27-03-2023
Publisher: AIP Publishing
Date: 14-03-2016
DOI: 10.1063/1.4944044
Abstract: Time-delayed collection field experiments are applied to planar organometal halide perovskite (CH3NH3PbI3) based solar cells to investigate charge carrier recombination in a fully working solar cell at the nanosecond to microsecond time scale. Recombination of mobile (extractable) charges is shown to follow second-order recombination dynamics for all fluences and time scales tested. Most importantly, the bimolecular recombination coefficient is found to be time-dependent, with an initial value of ca. 10−9 cm3/s and a progressive reduction within the first tens of nanoseconds. Comparison to the prototypical organic bulk heterojunction device PTB7:PC71BM yields important differences with regard to the mechanism and time scale of free carrier recombination.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6TA01087C
Abstract: We investigate the influence of solvent drenching in hybrid organic–inorganic perovskite (CH 3 NH 3 PbX) crystallization process with a non-solvent, toluene, during film fabrication process.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-12-2021
Abstract: The black, photoactive phase of formamidinium (FA) perovskites, which is usually stabilized by cation alloying to avoid the formation of inactive hexagonal phases, is assumed to be cubic. High-resolution microscopy studies by Doherty et al . using nanoscale probes revealed that these FA-rich phases are not cubic but rather undergo slight tilting (by two degrees) of the octahedra. Black phases can have localized regions of hexagonal phases that nucleate degradation. Surface-bound ethylenediaminetetraacetic acid stabilized the tilted phase of pure FA lead triiodide against environmental degradation. —PDS
Publisher: American Chemical Society (ACS)
Date: 22-06-2020
Publisher: Elsevier BV
Date: 04-2018
Publisher: Springer Science and Business Media LLC
Date: 31-08-2016
Publisher: Elsevier BV
Date: 12-2021
Publisher: Wiley
Date: 24-02-2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2EE03198A
Abstract: This work unveils periodic module rejuvenation as a new strategy to bring online the next-generation of perovskite tandem photovoltaic technologies earlier using experimental investigation and life cycle assessment modeling as an integrated tool.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TC01490D
Abstract: When halide perovskite light-emitting diodes are compressed, the electroluminesence weakens, which is explained by an increase in defect populations.
Publisher: American Chemical Society (ACS)
Date: 20-10-2020
Publisher: American Chemical Society (ACS)
Date: 15-09-2014
DOI: 10.1021/NN5036476
Abstract: Organic-inorganic metal halide perovskites have recently emerged as a top contender to be used as an absorber material in highly efficient, low-cost photovoltaic devices. Solution-processed semiconductors tend to have a high density of defect states and exhibit a large degree of electronic disorder. Perovskites appear to go against this trend, and despite relatively little knowledge of the impact of electronic defects, certified solar-to-electrical power conversion efficiencies of up to 17.9% have been achieved. Here, through treatment of the crystal surfaces with the Lewis bases thiophene and pyridine, we demonstrate significantly reduced nonradiative electron-hole recombination within the CH(3)NH(3)PbI(3-x)Cl(x) perovskite, achieving photoluminescence lifetimes which are enhanced by nearly an order of magnitude, up to 2 μs. We propose that this is due to the electronic passivation of under-coordinated Pb atoms within the crystal. Through this method of Lewis base passivation, we achieve power conversion efficiencies for solution-processed planar heterojunction solar cells enhanced from 13% for the untreated solar cells to 15.3% and 16.5% for the thiophene and pyridine-treated solar cells, respectively.
Publisher: American Physical Society (APS)
Date: 13-04-2022
Publisher: American Chemical Society (ACS)
Date: 31-10-2022
Publisher: American Association for the Advancement of Science (AAAS)
Date: 31-07-2020
Abstract: Scalable and high-efficiency perovskite tandem solar cells with long lifetime pave the way for sustainable photovoltaics.
Publisher: Springer Science and Business Media LLC
Date: 16-11-2016
DOI: 10.1038/SREP37167
Abstract: Semiconducting single-walled carbon nanotubes are one-dimensional materials with great prospects for applications such as optoelectronic and quantum information devices. Yet, their optical performance is hindered by low fluorescent yield. Highly mobile excitons interacting with quenching sites are attributed to be one of the main non-radiative decay mechanisms that shortens the exciton lifetime. In this paper we report on time-integrated photoluminescence measurements on in idual polymer wrapped semiconducting carbon nanotubes. An ultra narrow linewidth we observed demonstrates intrinsic exciton dynamics. Furthermore, we identify a state filling effect in in idual carbon nanotubes at cryogenic temperatures as previously observed in quantum dots. We propose that each of the CNTs is segmented into a chain of zero-dimensional states confined by a varying local potential along the CNT, determined by local environmental factors such as the amount of polymer wrapping. Spectral diffusion is also observed, which is consistent with the tunneling of excitons between these confined states.
Publisher: Wiley
Date: 27-05-2013
Abstract: We describe two methods in which we manipulate the binding of multiple conjugated polymers to single-walled carbon nanotubes (SWNTs) to produce new and novel nanostructures. One method fi rst utilizes the selective binding of poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) to a narrow distribution of semiconducting SWNTs and then uses a polymer exchange to transfer this purity to other nanotube-polymer combinations, using technologically useful polymers such as poly(3-hexylthiophene) (P3HT) and poly(9,9'-dioctylfluoreneco -benzothiadiazole) (F8BT) as fi rst ex les. The other method involves controlling the competitive binding of P3HT and F8BT to SWNTs to produce coaxial nanostructures consisting of both polymers simultaneously bound in ordered layers. We show that these two simple solution-processing techniques can be carried out sequentially to afford new dual-polymer nanostructures comprised of a semiconducting SWNT of a single chirality. This allows the favorable properties of both polymers and purified semiconducting SWNTs to be implemented into potentially highly efficient organic photovoltaic devices.
Publisher: American Chemical Society (ACS)
Date: 10-07-2018
DOI: 10.1021/ACS.NANOLETT.8B02190
Abstract: The easily tunable emission of halide perovskite nanocrystals throughout the visible spectrum makes them an extremely promising material for light-emitting applications. Whereas high quantum yields and long-term colloidal stability have already been achieved for nanocrystals emitting in the red and green spectral range, the blue region currently lags behind with low quantum yields, broad emission profiles, and insufficient colloidal stability. In this work, we present a facile synthetic approach for obtaining two-dimensional CsPbBr
Publisher: American Chemical Society (ACS)
Date: 17-07-2018
Publisher: Springer Science and Business Media LLC
Date: 24-06-2021
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Publisher: American Chemical Society (ACS)
Date: 29-01-2021
Publisher: Springer Science and Business Media LLC
Date: 03-10-2016
DOI: 10.1038/NMAT4765
Abstract: Metal halide perovskites such as methylammonium lead iodide (CH
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-06-2023
Abstract: Organic thin-film transistors (OTFTs) with ideal behavior are highly desired, because nonideal devices may overestimate the intrinsic property and yield inferior performance in applications. In reality, most polymer OTFTs reported in the literature do not exhibit ideal characteristics. Supported by a structure-property relationship study of several low-disorder conjugated polymers, here, we present an empirical selection rule for polymer candidates for textbook-like OTFTs with high reliability factors (100% for ideal transistors). The successful candidates should have low energetic disorder along their backbones and form thin films with spatially uniform energetic landscapes. We demonstrate that these requirements are satisfied in the semicrystalline polymer PffBT4T-2DT, which exhibits a reliability factor (~100%) that is exceptionally high for polymer devices, rendering it an ideal candidate for OTFT applications. Our findings broaden the selection of polymer semiconductors with textbook-like OTFT characteristics and would shed light upon the molecular design criteria for next-generation polymer semiconductors.
Publisher: American Chemical Society (ACS)
Date: 17-09-2020
Publisher: American Chemical Society (ACS)
Date: 26-11-2018
Publisher: Informa UK Limited
Date: 02-10-2022
Publisher: American Chemical Society (ACS)
Date: 22-05-2019
Publisher: American Chemical Society (ACS)
Date: 17-04-2023
Publisher: American Chemical Society (ACS)
Date: 22-09-2014
DOI: 10.1021/NL501982B
Abstract: Organic-inorganic perovskite solar cells have recently emerged at the forefront of photovoltaics research. Power conversion efficiencies have experienced an unprecedented increase to reported values exceeding 19% within just four years. With the focus mainly on efficiency, the aspect of stability has so far not been thoroughly addressed. In this paper, we identify thermal stability as a fundamental weak point of perovskite solar cells, and demonstrate an elegant approach to mitigating thermal degradation by replacing the organic hole transport material with polymer-functionalized single-walled carbon nanotubes (SWNTs) embedded in an insulating polymer matrix. With this composite structure, we achieve JV scanned power-conversion efficiencies of up to 15.3% with an average efficiency of 10 ± 2%. Moreover, we observe strong retardation in thermal degradation as compared to cells employing state-of-the-art organic hole-transporting materials. In addition, the resistance to water ingress is remarkably enhanced. These are critical developments for achieving long-term stability of high-efficiency perovskite solar cells.
Publisher: American Chemical Society (ACS)
Date: 15-05-2020
Publisher: Springer Science and Business Media LLC
Date: 13-12-2021
DOI: 10.1038/S41560-021-00941-3
Abstract: Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing ex les of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences.
Publisher: Wiley
Date: 19-10-2016
Abstract: The extent to which the soft structural properties of metal halide perovskites affect their optoelectronic properties is unclear. X-ray diffraction and micro-photoluminescence measurements are used to show that there is a coexistence of both tetragonal and orthorhombic phases through the low-temperature phase transition, and that cycling through this transition can lead to structural changes and enhanced optoelectronic properties.
Publisher: Springer Science and Business Media LLC
Date: 22-01-2020
DOI: 10.1038/S41560-019-0529-5
Abstract: Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis.
Publisher: American Chemical Society (ACS)
Date: 24-11-2010
DOI: 10.1021/NL1036484
Abstract: We have investigated the charge photogeneration dynamics at the interface formed between single-walled carbon nanotubes (SWNTs) and poly(3-hexylthiophene) (P3HT) using a combination of femtosecond spectroscopic techniques. We demonstrate that photoexcitation of P3HT forming a single molecular layer around a SWNT leads to an ultrafast (∼430 fs) charge transfer between the materials. The addition of excess P3HT leads to long-term charge separation in which free polarons remain separated at room temperature. Our results suggest that SWNT-P3HT blends incorporating only small fractions (1%) of SWNTs allow photon-to-charge conversion with efficiencies comparable to those for conventional (60:40) P3HT-fullerene blends, provided that small-diameter tubes are in idually embedded in the P3HT matrix.
Publisher: American Chemical Society (ACS)
Date: 20-11-2014
DOI: 10.1021/JZ5021795
Abstract: Here, we report the use of polymer-wrapped carbon nanotubes as a means to enhance charge extraction through undoped spiro-OMeTAD. With this approach a good solar cell performance is achieved without the implementation of conventional doping methods. We demonstrate that a stratified two-layer architecture of sequentially deposited layers of carbon nanotubes and spiro-OMeTAD, outperforms a conventional blend of the hole-conductor and the carbon nanotubes. We also provide insights into the mechanism of the rapid hole extraction observed in the two-layer approach.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-10-2013
Abstract: In the past 2 years, organolead halide perovskites have emerged as a promising class of light-harvesting media in experimental solar cells, but the physical basis for their efficiency has been unclear (see the Perspective by Hodes ). Two studies now show, using a variety of time-resolved absorption and emission spectroscopic techniques, that these materials manifest relatively long diffusion paths for charge carriers energized by light absorption. Xing et al. (p. 344 ) independently assessed (negative) electron and (positive) hole diffusion lengths and found them well-matched to one another to the ~100-nanometer optical absorption depth. Stranks et al. (p. 341 ) uncovered a 10-fold greater diffusion length in a chloride-doped material, which correlates with the material's particularly efficient overall performance. Both studies highlight effective carrier diffusion as a fruitful parameter for further optimization.
Publisher: Springer Science and Business Media LLC
Date: 24-05-2022
DOI: 10.1038/S41586-022-04872-1
Abstract: Understanding the nanoscopic chemical and structural changes that drive instabilities in emerging energy materials is essential for mitigating device degradation. The power conversion efficiency of halide perovskite photovoltaic devices has reached 25.7 per cent in single-junction and 29.8 per cent in tandem perovskite/silicon cells
Publisher: American Chemical Society (ACS)
Date: 20-04-2021
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
No related grants have been discovered for Sam Stranks.