ORCID Profile
0000-0001-7903-9642
Current Organisations
University of California, Berkeley
,
E O Lawrence Berkeley National Laboratory
,
University of Melbourne
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Photodetectors, Optical Sensors and Solar Cells | Nanoscale characterisation | Functional Materials | Nanotechnology | Electrical and Electronic Engineering | Nanophotonics | Nanotechnology | Functional materials | Photonics optoelectronics and optical communications |
Expanding Knowledge in Engineering | Instrumentation not elsewhere classified | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Technology |
Publisher: IEEE
Date: 06-2014
Publisher: IEEE
Date: 06-2014
Publisher: IEEE
Date: 06-2017
Publisher: American Physical Society (APS)
Date: 18-07-2022
Publisher: OSA
Date: 2019
Publisher: AIP Publishing
Date: 06-02-2015
DOI: 10.1063/1.4907804
Abstract: We investigate a recombination active grown-in defect limiting the bulk lifetime (τbulk) of high quality float-zone (FZ) p-type silicon wafers. After annealing the s les at temperatures between 80 °C and 400 °C, τbulk was found to increase from ∼500 μs to ∼1.5 ms. By isochronal annealing the p-type s les between 80 °C and 400 °C for 30 min, the annihilation energy (Eann) of the defect was determined to be 0.3 & Eann & 0.7 eV. When the annihilated s les were phosphorus gettered at 880 °C or subject to 0.2 sun illumination for 24 h, τbulk was found to degrade. However, when the s les were subsequently annealed at temperatures between 250 and 400 °C, the defect could be re-annihilated. The experimental results suggest that the defect limiting the lifetime in the p-type FZ silicon is not related to fast diffusing metallic impurities but rather to a lattice-impurity or an impurity-impurity metastable defect.
Publisher: Wiley
Date: 14-06-2013
Publisher: Wiley
Date: 04-05-2022
DOI: 10.1002/PIP.3574
Abstract: The year 2014 marks the point when silicon solar cells surpassed the 25% efficiency mark. Since then, all devices exceeding this mark, both small and large area, with contacts on both sides of the silicon wafer or just at the back, have utilized at least one passivating contact. Here, a passivating contact is defined as a group of layers that simultaneously provide selective conduction of charge carriers and effective passivation of the silicon surface. The widespread success of passivating contacts has prompted increased research into ways in which carrier‐selective junctions can be formed, yielding a erse range of approaches. This paper seeks to classify passivating contact solar cells into three families, according to the material used for charge‐carrier selection: doped amorphous silicon, doped polycrystalline silicon, and metal compounds/organic materials. The paper tabulates their current efficiency values, discusses distinctive features, advantages, and limitations, and highlights promising opportunities going forth towards even higher conversion efficiencies.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8EE03547D
Abstract: Solar-driven photocathode converts carbon dioxide to C 2 and C 3 products.
Publisher: Wiley
Date: 13-01-2023
Abstract: 2D materials, with distinct characteristics compared to their conventional bulk counterparts, have been a popular topic in various optoelectronic research fields. Herein, indium selenide (InSe), a monochalcogenide van der Waals layered semiconductor, which has been studied due to its thickness dependent optical characteristics is explored. For InSe to be used as a versatile light source, enhancing the emission of InSe is required. Here, enhanced photoluminescence (PL) from multi‐layer InSe is demonstrated using a gap plasmon induced between Ag nanocube dimer and an Au substrate. Such plasmonic structures support multiple resonances, one of those overlapping with InSe's band edge PL emission. The calculated Purcell factor shows a 200‐fold increase on the short edge of nanocube dimers. Experimentally, PL enhancement of 6‐fold is demonstrated at room temperature. In addition, a method for determining the thickness of 2D materials via dark‐field spectroscopy using white light illumination is shown. This study paves the way for the incorporation of 2D InSe into nanophotonic structures.
Publisher: Wiley
Date: 16-11-2016
Publisher: American Chemical Society (ACS)
Date: 21-09-2020
Publisher: Wiley
Date: 15-07-2014
Publisher: AIP Publishing
Date: 07-12-2016
DOI: 10.1063/1.4937732
Abstract: A sub-nm hydrogenated amorphous silicon (a-Si:H) film capped with silicon nitride (SiNx) is shown to provide a high level passivation to crystalline silicon (c-Si) surfaces. When passivated by a 0.8 nm a-Si:H/75 nm SiNx stack, recombination current density J0 values of 9, 11, 47, and 87 fA/cm2 are obtained on 10 Ω·cm n-type, 0.8 Ω·cm p-type, 160 Ω/sq phosphorus-diffused, and 120 Ω/sq boron-diffused silicon surfaces, respectively. The J0 on n-type 10 Ω·cm wafers is further reduced to 2.5 ± 0.5 fA/cm2 when the a-Si:H film thickness exceeds 2.5 nm. The passivation by the sub-nm a-Si:H/SiNx stack is thermally stable at 400 °C in N2 for 60 min on all four c-Si surfaces. Capacitance–voltage measurements reveal a reduction in interface defect density and film charge density with an increase in a-Si:H thickness. The nearly transparent sub-nm a-Si:H/SiNx stack is thus demonstrated to be a promising surface passivation and antireflection coating suitable for all types of surfaces encountered in high efficiency c-Si solar cells.
Publisher: IEEE
Date: 06-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2015
Publisher: AIP Publishing
Date: 19-03-2014
DOI: 10.1063/1.4869057
Abstract: Thermal SiO2 passivates both moderately and heavily doped silicon surfaces irrespective of the dopant type, which is advantageous in high-efficiency solar cell designs. Commercial photovoltaic cells are submitted to accelerated ageing tests, such as d -heat exposure, to ensure they maintain their performance for at least 20 yr. We find d -heat exposure causes a severe and rapid degradation of thermal SiO2 passivation on p+ silicon surfaces. The reaction is so severe that the diffused-region recombination in the degraded state is limited by the diffusion of minority carriers to the Si–SiO2 interface not the density of interface defects Dit. Certainly, this effect renders the thermal-oxide passivation useless if employed on a solar cell. To study the cause of the degradation, we also test the effects of storage in dry heat and room ambient conditions. Examination of the rate of degradation in the tested storage conditions in comparison with modelled diffusion of moisture in SiO2, we find a significant correlation between the time dependent J0e and moisture supplied to the interface, leading us to the conclusion that moisture ingression and subsequent reaction at the SiO2–Si interface are the cause of both d -heat and room- ambient degradation.
Publisher: IEEE
Date: 06-2013
Publisher: American Chemical Society (ACS)
Date: 09-05-2018
DOI: 10.1021/ACSSENSORS.7B00961
Abstract: Wearable sweat sensing is a rapidly rising research area driven by its promising potential in health, fitness, and diagnostic applications. Despite the growth in the field, major challenges in relation to sweat metrics remain to be addressed. These challenges include sweat rate monitoring for its complex relation with sweat compositions and sweat s ling for sweat dynamics studies. In this work, we present a flexible microfluidic sweat sensing patch that enhances real-time electrochemical sensing and sweat rate analysis via sweat s ling. The device contains a spiral-patterned microfluidic component that is embedded with ion-selective sensors and an electrical impedance-based sweat rate sensor on a flexible plastic substrate. The patch is enabled to autonomously perform sweat analysis by interfacing the sensing component with a printed circuit board that is capable of on-site signal conditioning, analysis, and transmission. Progressive sweat flow in the microfluidic device, governed by the pressure induced by the secreted sweat, enhances sweat s ling and electrochemical detection via a defined sweat collection chamber and a directed sweat route. The characteristic of the sweat rate sensor is validated through a theoretical simulation, and the precision and accuracy of the flow rate is verified with a commercial syringe pump and a Macroduct sweat collector. On-body simultaneous monitoring of ion (H
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2017
Publisher: American Chemical Society (ACS)
Date: 06-2016
Abstract: In this study, we present a novel application of thin magnesium fluoride films to form electron-selective contacts to n-type crystalline silicon (c-Si). This allows the demonstration of a 20.1%-efficient c-Si solar cell. The electron-selective contact is composed of deposited layers of amorphous silicon (∼6.5 nm), magnesium fluoride (∼1 nm), and aluminum (∼300 nm). X-ray photoelectron spectroscopy reveals a work function of 3.5 eV at the MgF2/Al interface, significantly lower than that of aluminum itself (∼4.2 eV), enabling an Ohmic contact between the aluminum electrode and n-type c-Si. The optimized contact structure exhibits a contact resistivity of ∼76 mΩ·cm(2), sufficiently low for a full-area contact to solar cells, together with a very low contact recombination current density of ∼10 fA/cm(2). We demonstrate that electrodes functionalized with thin magnesium fluoride films significantly improve the performance of silicon solar cells. The novel contacts can potentially be implemented also in organic optoelectronic devices, including photovoltaics, thin film transistors, or light emitting diodes.
Publisher: Wiley
Date: 30-10-2023
Publisher: Wiley
Date: 29-08-2013
Publisher: Wiley
Date: 25-05-2016
Publisher: American Chemical Society (ACS)
Date: 09-08-2021
Publisher: IEEE
Date: 06-2017
Publisher: American Chemical Society (ACS)
Date: 08-11-2017
Abstract: Black phosphorus (b-P) and more recently black phosphorus-arsenic alloys (b-PAs) are candidate 2D materials for the detection of mid-wave and potentially long-wave infrared radiation. However, studies to date have utilized laser-based measurements to extract device performance and the responsivity of these detectors. As such, their performance under thermal radiation and spectral response has not been fully characterized. Here, we perform a systematic investigation of gated-photoconductors based on b-PAs alloys as a function of thickness over the composition range of 0-91% As. Infrared transmission and reflection measurements are performed to determine the bandgap of the various compositions. The spectrally resolved photoresponse for various compositions in this material system is investigated to confirm absorption measurements, and we find that the cutoff wavelength can be tuned from 3.9 to 4.6 μm over the studied compositional range. In addition, we investigated the temperature-dependent photoresponse and performed calibrated responsivity measurements using blackbody flood illumination. Notably, we find that the specific detectivity (D*) can be optimized by adjusting the thickness of the b-P/b-PAs layer to maximize absorption and minimize dark current. We obtain a peak D* of 6 × 10
Publisher: Wiley
Date: 21-06-2023
Abstract: Flexible optoelectronics is a rapidly growing field, with a wide range of potential applications. From wearable sensors to bendable solar cells, curved displays, and curved focal plane arrays, the possibilities are endless. The criticality of flexible photodetectors for many of these applications is acknowledged, however, devices that are demonstrated thus far are limited in their spectral range. In this study, flexible photodetectors are demonstrated using a VO x nanoparticle ink, with an extremely broad operating wavelength range of 0.4 to 20 µm. This ink is synthesized using a simple and scalable wet‐chemical process. These photodetectors operate at room temperature and exhibit minimal variance in performance even when bent at angles of up to 100 ° at a bend radius of 6.4 mm. In addition, rigorous strain testing of 100 bend and release cycles revealed a photoresponse with a standard deviation of only 0.55%. This combination of mechanical flexibility, wide spectral response, and ease of fabrication makes these devices highly desirable for a wide range of applications, including low‐cost wearable sensors and hyperspectral imaging systems.
Publisher: AIP Publishing
Date: 08-12-2014
DOI: 10.1063/1.4903467
Abstract: This letter examines the application of transparent MoOx (x & 3) films deposited by thermal evaporation directly onto crystalline silicon (c-Si) to create hole-conducting contacts for silicon solar cells. The carrier-selectivity of MoOx based contacts on both n- and p-type surfaces is evaluated via simultaneous consideration of the contact recombination parameter J0c and the contact resistivity ρc. Contacts made to p-type wafers and p+ diffused regions achieve optimum ρc values of 1 and 0.2 mΩ·cm2, respectively, and both result in a J0c of ∼200 fA/cm2. These values suggest that significant gains can be made over conventional hole contacts to p-type material. Similar MoOx contacts made to n-type silicon result in higher J0c and ρc with optimum values of ∼300 fA/cm2 and 30 mΩ·cm2 but still offer significant advantages over conventional approaches in terms of contact passivation, optical properties, and device fabrication.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7EE01764B
Abstract: In a process analogous to natural photosynthesis, solar-driven reduction of carbon dioxide to hydrocarbon and oxygenate products is demonstrated with an overall efficiency exceeding 5%.
Publisher: American Chemical Society (ACS)
Date: 31-08-2016
Abstract: The reduction of parasitic recombination processes commonly occurring within the silicon crystal and at its surfaces is of primary importance in crystalline silicon devices, particularly in photovoltaics. Here we explore a simple, room temperature treatment, involving a nonaqueous solution of the superacid bis(trifluoromethane)sulfonimide, to temporarily deactivate recombination centers at the surface. We show that this treatment leads to a significant enhancement in optoelectronic properties of the silicon wafer, attaining a level of surface passivation in line with state-of-the-art dielectric passivation films. Finally, we demonstrate its advantage as a bulk lifetime and process cleanliness monitor, establishing its compatibility with large area photoluminescence imaging in the process.
Publisher: AIP Publishing
Date: 18-05-2015
DOI: 10.1063/1.4921416
Abstract: This letter reports effective passivation of crystalline silicon (c-Si) surfaces by thermal atomic layer deposited tantalum oxide (Ta2O5) underneath plasma enhanced chemical vapour deposited silicon nitride (SiNx). Cross-sectional transmission electron microscopy imaging shows an approximately 2 nm thick interfacial layer between Ta2O5 and c-Si. Surface recombination velocities as low as 5.0 cm/s and 3.2 cm/s are attained on p-type 0.8 Ω·cm and n-type 1.0 Ω·cm c-Si wafers, respectively. Recombination current densities of 25 fA/cm2 and 68 fA/cm2 are measured on 150 Ω/sq boron-diffused p+ and 120 Ω/sq phosphorus-diffused n+ c-Si, respectively. Capacitance–voltage measurements reveal a negative fixed insulator charge density of −1.8 × 1012 cm−2 for the Ta2O5 film and −1.0 × 1012 cm−2 for the Ta2O5/SiNx stack. The Ta2O5/SiNx stack is demonstrated to be an excellent candidate for surface passivation of high efficiency silicon solar cells.
Publisher: Springer Science and Business Media LLC
Date: 27-08-2018
Publisher: AIP Publishing
Date: 16-03-2015
DOI: 10.1063/1.4915326
Abstract: Minimizing carrier recombination at cell contacts becomes increasingly important for reaching high efficiency. In this work, the passivated contact concept is implemented into n-type silicon solar cells with laser-processed local back surface fields. The passivation and contact characteristics of the SiO2/amorphous silicon (a-Si:H) stack on localized laser doped n+ regions are investigated. We find that the SiO2/a-Si:H stack provides not only good passivation to laser doped n+ regions but also allows a low contact resistivity after thermal annealing. With the implementation of the SiO2/a-Si:H passivated contact, an absolute efficiency gain of up to 1.5% is achieved for n-type solar cells.
Publisher: Elsevier BV
Date: 08-2016
Publisher: American Chemical Society (ACS)
Date: 14-08-2019
Publisher: American Chemical Society (ACS)
Date: 24-04-2019
Abstract: In order to achieve a high performance-to-cost ratio to photovoltaic devices, the development of crystalline silicon (c-Si) solar cells with thinner substrates and simpler fabrication routes is an important step. Thin-film heterojunction solar cells (HSCs) with dopant-free and carrier-selective configurations look like ideal candidates in this respect. Here, we investigated the application of n-type silicon oly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HSCs on periodic nanopyramid textured, ultrathin c-Si (∼25 μm) substrates. A fluorine-doped titanium oxide film was used as an electron-selective passivating layer showing excellent interfacial passivation (surface recombination velocity ∼10 cm/s) and contact property (contact resistivity ∼20 mΩ/cm
Publisher: IEEE
Date: 06-2018
Publisher: Elsevier BV
Date: 09-2018
Publisher: Informa UK Limited
Date: 31-01-2019
Publisher: Wiley
Date: 26-10-2023
Abstract: This article presents a comprehensive study regarding the impact of the Al electrode on the surface passivation of three TiO x ‐based passivating selective contacts: TiO x :Al/LiF x /Al,TiO x /LiF x /Al, and a‐Si/TiO x :Al/LiF x /Al. A deterioration in passivation is recorded after the deposition of the Al electrode at close to room temperature, where the deterioration correlated to the Al thickness. A thin Al (10 nm) electrode resulted in the most severe passivation decline, while s les with a 100 nm Al electrode showed much less passivation deterioration. Furthermore, it is found that a low‐temperature annealing step led to a partial recovery of the passivation, particularly in the case of TiO x :Al/LiF x /Al and a‐Si/TiO x :Al/LiF x /Al contacts. The presented discovery in this article provides crucial insight into the importance of characterization and evaluation of passivating contacts, which is demonstrated here to be highly sensitive to the deposited metal thickness and the interfacial layers, as well as to the post‐deposition annealing.
Publisher: Springer Science and Business Media LLC
Date: 16-09-2019
Publisher: Wiley
Date: 03-02-2017
Publisher: Springer Science and Business Media LLC
Date: 25-01-2016
Publisher: IEEE
Date: 20-06-2021
Publisher: Optica Publishing Group
Date: 2020
DOI: 10.1364/CLEOPR.2020.C11E_5
Abstract: We demonstrate long wave infrared photodetectors based on the transition metal dichalcogenide platinum diselenide (PtSe 2 ) in its bulk form for the first time to our knowledge. Fabricated devices show sub-millisecond response times.
Publisher: American Chemical Society (ACS)
Date: 17-05-2016
Publisher: AIP Publishing
Date: 28-10-2014
DOI: 10.1063/1.4900539
Abstract: Carrier recombination at the metal-semiconductor contacts has become a significant obstacle to the further advancement of high-efficiency diffused-junction silicon solar cells. This paper provides the proof-of-concept of a procedure to reduce contact recombination by means of enhanced metal-insulator-semiconductor (MIS) structures. Lightly diffused n+ and p+ surfaces are passivated with SiO2/a-Si:H and Al2O3/a-Si:H stacks, respectively, before the MIS contacts are formed by a thermally activated alloying process between the a-Si:H layer and an overlying aluminum film. Transmission/scanning transmission electron microscopy (TEM/STEM) and energy dispersive x-ray spectroscopy are used to ascertain the nature of the alloy. Idealized solar cell simulations reveal that MIS(n+) contacts, with SiO2 thicknesses of ∼1.55 nm, achieve the best carrier-selectivity producing a contact resistivity ρc of ∼3 mΩ cm2 and a recombination current density J0c of ∼40 fA/cm2. These characteristics are shown to be stable at temperatures up to 350 °C. The MIS(p+) contacts fail to achieve equivalent results both in terms of thermal stability and contact characteristics but may still offer advantages over directly metallized contacts in terms of manufacturing simplicity.
Publisher: IEEE
Date: 06-2015
Publisher: AIP Publishing
Date: 24-06-2019
DOI: 10.1063/1.5097825
Abstract: Two-dimensional (2D) noble-metal dichalcogenides exhibit exceptionally strong thickness-dependent bandgaps, which can be leveraged in a wide variety of device applications. A detailed study of their optical (e.g., optical bandgaps) and electrical properties (e.g., mobilities) is important in determining potential future applications of these materials. In this work, we perform detailed optical and electrical characterization of 2D PdSe2 nanoflakes mechanically exfoliated from a single-crystalline source. Layer-dependent bandgap analysis from optical absorption results indicates that this material is an indirect semiconductor with bandgaps of approximately 1.37 and 0.50 eV for the monolayer and bulk, respectively. Spectral photoresponse measurements further confirm these bandgap values. Moreover, temperature-dependent electrical measurements of a 6.8-nm-thick PdSe2 flake-based transistor show effective electron mobilities of 130 and 520 cm2 V−1 s−1 at 300 K and 77 K, respectively. Finally, we demonstrate that PdSe2 can be utilized for short-wave infrared photodetectors. A room-temperature specific detectivity (D*) of 1.8 × 1010 cm Hz1/2 W−1 at 1 μm with a band edge at 1.94 μm is achieved on a 6.8-nm-thick PdSe2 flake-based photodetector.
Publisher: American Chemical Society (ACS)
Date: 08-12-2017
Publisher: IEEE
Date: 06-2017
Publisher: Springer Science and Business Media LLC
Date: 25-03-2020
DOI: 10.1038/S41598-020-61998-W
Abstract: In recent years there has been much interest concerning the development of modulators in the mid- to long-wave infrared, based on emerging materials such as graphene. These have been frequently pursued for optical communications, though also for other specialized applications such as infrared scene projectors. Here we investigate a new application for graphene modulators in the mid- to long-wave infrared. We demonstrate, for the first time, computational spectroscopy in the mid- to long-wave infrared using a graphene-based metasurface modulator. Furthermore, our metasurface device operates at low gate voltage. To demonstrate computational spectroscopy, we provide our algorithm with the measured reflection spectra of the modulator at different gate voltages. We also provide it with the measured reflected light power as a function of the gate voltage. The algorithm then estimates the input spectrum. We show that the reconstructed spectrum is in good agreement with that measured directly by a Fourier transform infrared spectrometer, with a normalized mean-absolute-error (NMAE) of 0.021.
Publisher: American Chemical Society (ACS)
Date: 25-01-2018
Publisher: Wiley
Date: 17-11-2016
DOI: 10.1002/PIP.2838
Publisher: American Chemical Society (ACS)
Date: 18-06-2018
Abstract: Two-dimensional (2D) materials, particularly black phosphorus (bP), have demonstrated themselves to be excellent candidates for high-performance infrared photodetectors and transistors. However, high-quality bP can be obtained only via mechanical exfoliation from high-temperature- and high-pressure-grown bulk crystals and degrades rapidly when exposed to ambient conditions. Here, we report solution-synthesized and air-stable quasi-2D tellurium (Te) nanoflakes for short-wave infrared (SWIR) photodetectors. We perform comprehensive optical characterization via polarization-resolved transmission and reflection measurements and report the absorbance and complex refractive index of Te crystals. It is found that this material is an indirect semiconductor with a band gap of 0.31 eV. From temperature-dependent electrical measurements, we confirm this band-gap value and find that 12 nm thick Te nanoflakes show high hole mobilities of 450 and 1430 cm
Publisher: Wiley
Date: 29-12-2021
Abstract: 2D materials, such as graphene, transition metal dichalcogenides, black phosphorus, and tellurium, have been demonstrated to be promising building blocks for the fabrication of next‐generation high‐performance infrared (IR) photodetectors with erse device architectures and impressive device performance. Integrating IR photodetectors with nanophotonic structures, such as surface plasmon structures, optical waveguides, and optical cavities, has proven to be a promising strategy to maximize the light absorption of 2D absorbers, thus enhancing the detector performance. In this review, the state‐of‐the‐art progress of IR photodetectors is comprehensively summarized based on 2D materials and nanophotonic structures. First, the advantages of using 2D materials for IR photodetectors are discussed. Following that, 2D material‐based IR detectors are classified based on their composition, and their detection mechanisms, key figures‐of‐merit, and the principle of absorption enhancement are discussed using nanophotonic approaches. Then, recent advances in 2D material‐based IR photodetectors are reviewed, categorized by device architecture, i.e., photoconductors, van der Waals heterojunctions, and hybrid systems consisting of 2D materials and nanophotonic structures. The review is concluded by providing perspectives on the challenges and future directions of this field.
Publisher: Wiley
Date: 28-05-2018
Publisher: AIP Publishing
Date: 12-09-2016
DOI: 10.1063/1.4962960
Abstract: Among the metals, magnesium has one of the lowest work functions, with a value of 3.7 eV. This makes it very suitable to form an electron-conductive cathode contact for silicon solar cells. We present here the experimental demonstration of an amorphous silicon/magnesium/aluminium (a-Si:H/Mg/Al) passivating contact for silicon solar cells. The conduction properties of a thermally evaporated Mg/Al contact structure on n-type crystalline silicon (c-Si) are investigated, achieving a low resistivity Ohmic contact to moderately doped n-type c-Si (∼5 × 1015 cm−3) of ∼0.31 Ω cm2 and ∼0.22 Ω cm2 for s les with and without an amorphous silicon passivating interlayer, respectively. Application of the passivating cathode to the whole rear surface of n-type front junction c-Si solar cells leads to a power conversion efficiency of 19% in a proof-of-concept device. The low thermal budget of the cathode formation, its dopant-less nature, and the simplicity of the device structure enabled by the Mg/Al contact open up possibilities in designing and fabricating low-cost silicon solar cells.
Publisher: AIP Publishing
Date: 17-07-2023
DOI: 10.1063/5.0156171
Abstract: We present an approach to selectively examine an asymmetric potential in the buried layer of solar cell devices by means of nonlinear x-ray spectroscopy. Detecting second harmonic generation signals while resonant to the SiO2 core level, we directly observe existence of the band bending effect in the SiO2 nanolayer, buried in the heterostructures of Al/LiF/SiO2/Si, TiO2/SiO2/Si, and Al2O3/SiO2/Si. The results demonstrate high sensitivity of the method to the asymmetric potential that determines performance of functional materials for photovoltaics or other optoelectronic devices.
Publisher: Elsevier BV
Date: 07-2015
Publisher: OSA
Date: 2018
Publisher: American Chemical Society (ACS)
Date: 29-07-2019
DOI: 10.26434/CHEMRXIV.8145986.V2
Abstract: Strategic design of experiments combined with machine learning is used to optimize the synthesis of p-type transparent conductors.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2015
Publisher: AIP Publishing
Date: 24-04-2014
DOI: 10.1063/1.4872262
Abstract: Carrier recombination at the metal contacts is a major obstacle in the development of high-performance crystalline silicon homojunction solar cells. To address this issue, we insert thin intrinsic hydrogenated amorphous silicon [a-Si:H(i)] passivating films between the dopant-diffused silicon surface and aluminum contacts. We find that with increasing a-Si:H(i) interlayer thickness (from 0 to 16 nm) the recombination loss at metal-contacted phosphorus (n+) and boron (p+) diffused surfaces decreases by factors of ∼25 and ∼10, respectively. Conversely, the contact resistivity increases in both cases before saturating to still acceptable values of ∼ 50 mΩ cm2 for n+ and ∼100 mΩ cm2 for p+ surfaces. Carrier transport towards the contacts likely occurs by a combination of carrier tunneling and aluminum spiking through the a-Si:H(i) layer, as supported by scanning transmission electron microscopy–energy dispersive x-ray maps. We explain the superior contact selectivity obtained on n+ surfaces by more favorable band offsets and capture cross section ratios of recombination centers at the c-Si/a-Si:H(i) interface.
Publisher: IEEE
Date: 06-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2015
Publisher: Elsevier BV
Date: 09-2015
Publisher: Elsevier BV
Date: 08-2015
Publisher: Wiley
Date: 07-05-2022
Abstract: Advanced doped‐silicon‐layer‐based passivating contacts have boosted the power conversion efficiency (PCE) of single‐junction crystalline silicon ( c ‐Si) solar cells to over 26%. However, the inevitable parasitic light absorption of the doped silicon layers impedes further PCE improvement. To this end, alternative passivating contacts based on wide‐bandgap metal compounds (so‐called dopant‐free passivating contacts (DFPCs)) have attracted great attention, thanks to their potential merits in terms of parasitic absorption loss, ease‐of‐deposition, and cost. Intensive research activity has surrounded this topic with significant progress made in recent years. Various electron‐selective and hole‐selective contacts based on metal compounds have been successfully developed, and a ch ion PCE of 23.5% has been achieved for a c ‐Si solar cell with a MoO x ‐based hole‐selective contact. In this work, the fundamentals and development status of DFPCs are reviewed and the challenges and potential solutions for enhancing the carrier selectivity of DFPCs are discussed. Based on comprehensive and in‐depth analysis and simulations, the improvement strategies and future prospects for DFPCs design and device implementation are pointed out. By tuning the carrier concentration of the metal compound and the work function of the capping transparent electrode, high PCEs over 26% can be achieved for c ‐Si solar cells with DFPCs.
Publisher: Elsevier BV
Date: 11-2015
Publisher: Wiley
Date: 08-10-2015
Publisher: Wiley
Date: 18-01-2019
Publisher: IEEE
Date: 06-2016
Publisher: IEEE
Date: 06-2018
Publisher: Wiley
Date: 16-03-2022
DOI: 10.1002/PIP.3552
Abstract: Solar cells rely on the efficient generation of electrons and holes and the subsequent collection of these photoexcited charge carriers at spatially separated electrodes. High wafer quality is now commonplace for crystalline silicon ( c ‐Si) based solar cells, meaning that the cell's efficiency potential is largely dictated by the effectiveness of its carrier‐selective contacts. The majority of contacts currently employed in industrial production are based on highly doped‐silicon, which can introduce negative side‐effects including Auger recombination or parasitic absorption depending on whether the dopants are diffused into the absorber or whether they are incorporated into silicon layers deposited outside the absorber. Given the terawatt scale of deployment of c ‐Si solar cells, the search for alternative contacting schemes that can offer potential benefits in terms of performance, cost, ease of processing or stability is highly relevant. One such category of contacting schemes, with the potential to avoid the above mentioned issues, is that which employs metal compounds as the ‘carrier‐selective’ layer. The last 7 years has seen a surge in interest on this topic and a few promising families of materials have emerged, most prominently the alkali/alkaline‐earth metal compounds and the transition‐metal oxides. The number of successful selective‐contact demonstrations of materials within these families is fast increasing with the best solar cell demonstrations now exceeding 23%. However, in addition to improving their efficiency performance, several challenges remain if such contacts are to be considered for industrial adoption. These are mainly associated with poor stability, lack of compatibility with transparent electrodes and inability to be deposited using standard industrial techniques. This review covers the historical developments, current status and future prospects of metal‐compound based selective contacts in the context of c ‐Si photovoltaics.
Publisher: Springer Science and Business Media LLC
Date: 09-01-2023
Publisher: American Chemical Society (ACS)
Date: 15-06-2023
Publisher: Elsevier BV
Date: 03-2020
Publisher: Wiley
Date: 03-10-2022
Abstract: Atomically thin two‐dimensional (2D) transition metal dichalcogenides (TMDs) are promising materials for photovoltaic (PV) applications. Their self‐terminated nature and strong absorption characteristics introduce an unprecedented possibility for high voltages to bandgap ratios, with secondary benefits including the potential for high internal quantum efficiencies/low recombination and strong absorption coefficients coupled with stability in a range of environments. However, despite the promise of such material systems, their PV performances still lag behind the conventional 3D materials. In principle, one possible way to manipulate the behavior of a 2D heterobilayer structure is to change its interlayer twist angle. In this study, the effects of twist angle between vertically stacked type‐II MoS 2 /WS 2 heterobilayers on fundamental optical properties such as light absorbance, excess carrier lifetime, and diffusion are reported. These properties can have a direct effect on the final PV performance of these heterobilayers. It is found that the interlayer twist in MoS 2 /WS 2 heterobilayers does not affect their absorbance. However, the carrier lifetime and photon emission across the heterobilayers are modulated with the interlayer twist. These findings could be useful to facilitate the optimization of monolayer TMD‐based optoelectronic devices.
Publisher: The R Foundation
Date: 2019
DOI: 10.32614/RJ-2019-002
Publisher: American Chemical Society (ACS)
Date: 22-03-2021
Publisher: IEEE
Date: 21-06-2021
Publisher: Elsevier BV
Date: 04-2021
Publisher: Optica Publishing Group
Date: 2020
DOI: 10.1364/CLEOPR.2020.C11B_4
Abstract: We demonstrate room-temperature photodetectors at wavelengths from visible (450 nm, 532 nm) to near- (850 nm), short-wave (1550 nm), mid-wave (4.5 µm) and long-wave (8.35 µm) infrared. These are based on drop-cast Cu TCNQ crystals.
Publisher: American Chemical Society (ACS)
Date: 15-09-2021
Publisher: Springer Science and Business Media LLC
Date: 02-07-2020
DOI: 10.1038/S41598-020-67682-3
Abstract: The almond cake is a protein-rich residue generated by the mechanical expression of the almond oil. The effects of the aqueous (AEP) and enzyme-assisted aqueous extraction processes (EAEP) on the biological properties of the almond cake protein were evaluated. Total phenolic content (TPC), antioxidant capacity, inhibitory effects against crucial enzymes related to metabolic syndrome, antimicrobial potential, and in vitro protein digestibility profile were assessed. EAEP provided the best results for antioxidant capacity by both ORAC (397.2 µmol TE per g) and ABTS (650.5 µmol TE per g) methods and also showed a high (~ 98%) potential for α-glucosidase inhibition. The AEP resulted in protein extracts with the highest lipase inhibition (~ 70%) in a dose-dependent way. Enzymatic kinetic analyses revealed that EAEP generated uncompetitive inhibitors against α-glucosidase, while EAEP, AEP, and HEX-AEP (used as control) generated the same kind of inhibitors against lipase. No protein extract was effective against any of the bacteria strains tested at antimicrobial assays. An in silico theoretical hydrolysis of amandin subunits corroborated with the results found for antioxidant capacity, enzyme inhibitory experiments, and antimicrobial activity. Digestibility results indicated that the digestive proteases used were efficient in hydrolyzing almond proteins, regardless of the extraction applied and that HEX-AEP presented the highest digestibility (85%). In summary, EAEP and AEP skim proteins have the potential to be used as a nutraceutical ingredient. The biological properties observed in these extracts could help mitigate the development of metabolic syndrome where EAEP and AEP skim proteins could be potentially used as a prophylactic therapy for diabetes and obesity, respectively.
Publisher: American Chemical Society (ACS)
Date: 11-02-2016
DOI: 10.1021/ACS.NANOLETT.5B05124
Abstract: P-type transparent conducting films of nanocrystalline (CuS)x:(ZnS)1-x were synthesized by facile and low-cost chemical bath deposition. Wide angle X-ray scattering (WAXS) and high resolution transmission electron microscopy (HRTEM) were used to evaluate the nanocomposite structure, which consists of sub-5 nm crystallites of sphalerite ZnS and covellite CuS. Film transparency can be controlled by tuning the size of the nanocrystallites, which is achieved by adjusting the concentration of the complexing agent during growth optimal films have optical transmission above 70% in the visible range of the spectrum. The hole conductivity increases with the fraction of the covellite phase and can be as high as 1000 S cm(-1), which is higher than most reported p-type transparent materials and approaches that of n-type transparent materials such as indium tin oxide (ITO) and aluminum doped zinc oxide (AZO) synthesized at a similar temperature. Heterojunction p-(CuS)x:(ZnS)1-x/n-Si solar cells were fabricated with the nanocomposite film serving as a hole-selective contact. Under 1 sun illumination, an open circuit voltage of 535 mV was observed. This value compares favorably to other emerging heterojunction Si solar cells which use a low temperature process to fabricate the contact, such as single-walled carbon nanotube/Si (370-530 mV) and graphene/Si (360-552 mV).
Publisher: Wiley
Date: 12-12-2017
Publisher: Springer Science and Business Media LLC
Date: 23-08-2018
DOI: 10.1038/S41598-018-31053-W
Abstract: In this study, the thermal stability of a contact structure featuring hole-selective tungsten oxide (WO x ) and aluminum deposited onto p -type crystalline silicon (c-Si/WO x /Al) was investigated using a combination of transmission line measurements (TLM) and in situ transmission electron microscopy (TEM) studies. The TEM images provide insight into why the charge carrier transport and recombination characteristics change as a function of temperature, particularly as the s les are annealed at temperatures above 500 °C. In the as-deposited state, a ≈ 2 nm silicon oxide (SiO x ) interlayer forms at the c-Si/WO x interface and a ≈ 2–3 nm aluminum oxide (AlO x ) interlayer at the WO x /Al interface. When annealing above 500 °C, Al diffusion begins, and above 600 °C complete intermixing of the SiO x , WO x , AlO x and Al layers occurs. This results in a large drop in the contact resistivity, but is the likely reason surface recombination increases at these high temperatures, since a c-Si/Al contact is basically being formed. This work provides some fundamental insight that can help in the development of WO x films as hole-selective rear contacts for p -type solar cells. Furthermore, this study demonstrates that in situ TEM can provide valuable information about thermal stability of transition metal oxides functioning as carrier-selective contacts in silicon solar cells.
Publisher: Wiley
Date: 06-03-2019
Publisher: AIP Publishing
Date: 14-05-2018
DOI: 10.1063/1.5032226
Abstract: This letter reports effective passivation of crystalline silicon (c-Si) surfaces by thermal atomic layer deposited zirconium oxide (ZrOx). The optimum layer thickness and activation annealing conditions are determined to be 20 nm and 300 °C for 20 min. Cross-sectional transmission electron microscopy imaging shows an approximately 1.6 nm thick SiOx interfacial layer underneath an 18 nm ZrOx layer, consistent with ellipsometry measurements (∼20 nm). Capacitance–voltage measurements show that the annealed ZrOx film features a low interface defect density of 1.0 × 1011 cm−2 eV−1 and a low negative film charge density of −6 × 1010 cm−2. Effective lifetimes of 673 μs and 1.1 ms are achieved on p-type and n-type 1 Ω cm undiffused c-Si wafers, respectively, corresponding to an implied open circuit voltage above 720 mV in both cases. The results demonstrate that surface passivation quality provided by ALD ZrOx is consistent with the requirements of high efficiency silicon solar cells.
Publisher: American Chemical Society (ACS)
Date: 04-03-2019
Abstract: The reduction of carrier recombination processes by surface passivation is vital for highly efficient crystalline silicon (c-Si) solar cells and bulk wafer metrological characterization. Herein, we report a dip coating passivation of silicon surfaces in ambient air and temperature with Nafion, achieving a ch ion effective carrier lifetime of 12 ms on high resistivity n-type c-Si, which is comparable to state-of-the-art passivation methods. Nafion is a nonreactive polymer with strong Lewis acidity, thus leading to the formation of a large density of fixed charges at silicon surface, 1-2 orders of magnitude higher than what is achievable with conventional thin-film passivation layers. Notably, Nafion passivates the c-Si surface only by the fixed charges without chemical modification of dangling bonds, which is fundamentally different from the common practice of combining chemical with field-effect passivation. This dip coating process is simple and robust, without the need for complex equipment or parameter optimization as there is no chemical reaction involved.
Publisher: AIP Publishing
Date: 08-2016
DOI: 10.1063/1.4960529
Abstract: This work explores the application of transparent nitrogen doped copper oxide (CuOx:N) films deposited by reactive sputtering to create hole-selective contacts for p-type crystalline silicon (c-Si) solar cells. It is found that CuOx:N sputtered directly onto crystalline silicon is able to form an Ohmic contact. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are used to characterise the structural and physical properties of the CuOx:N films. Both the oxygen flow rate and the substrate temperature during deposition have a significant impact on the film composition, as well as on the resulting contact resistivity. After optimization, a low contact resistivity of ∼10 mΩ cm2 has been established. This result offers significant advantages over conventional contact structures in terms of carrier transport and device fabrication.
Publisher: IEEE
Date: 06-2014
Publisher: The Electrochemical Society
Date: 2012
DOI: 10.1149/2.020205JSS
Publisher: Wiley
Date: 20-11-2023
Abstract: Photodetectors formed with layered two‐dimensional (2D) materials have shown significant potential for integration with photonic circuits, offering fast, high responsivity and low noise detection over a broad range of optical wavelengths. However, only preliminary trials of this concept have been performed on emerging photonics platforms such as lithium niobate on insulator (LNOI). In this study, a novel architecture consisting of ≈15 nm thick layered black phosphorus (bP) photoconductors draped over LNOI waveguides is demonstrated. The performance of these detectors is studied across the telecom bands at room temperature, and a high extrinsic responsivity of 148 mA W −1 is measured at λ = 1550 nm under low bias conditions ( V DS = 0.3 V). The spectral response of the detectors is broad allowing the response of other photonic components, such as fiber‐to‐chip grating couplers, to be characterized in situ, without need to out‐couple the light. Finally, the speed of the bP detectors is found to be beyond our instrumentation, setting 100 ns as an upper‐limit rise/fall time, with the actual speed of the bP detector likely to be much faster.
Publisher: IEEE
Date: 06-2015
Publisher: American Chemical Society (ACS)
Date: 25-03-2021
Publisher: Springer Science and Business Media LLC
Date: 22-08-2017
DOI: 10.1038/S41598-017-08913-Y
Abstract: There is tremendous interest in reducing losses caused by the metal contacts in silicon photovoltaics, particularly the optical and resistive losses of the front metal grid. One commonly sought-after goal is the creation of high aspect-ratio metal fingers which provide an optically narrow and low resistance pathway to the external circuit. Currently, the most widely used metal contact deposition techniques are limited to widths and aspect-ratios of ~40 μm and ~0.5, respectively. In this study, we introduce the use of a micropatterned polydimethylsiloxane encapsulation layer to form narrow (~20 μm) microchannels, with aspect-ratios up to 8, on the surface of solar cells. We demonstrate that low temperature metal pastes, electroless plating and atomic layer deposition can all be used within the microchannels. Further, we fabricate proof-of-concept structures including simple planar silicon heterojunction and homojunction solar cells. While preliminary in both design and efficiency, these results demonstrate the potential of this approach and its compatibility with current solar cell architectures.
Publisher: IEEE
Date: 06-2019
Publisher: Elsevier BV
Date: 11-2015
Publisher: IEEE
Date: 06-2017
Publisher: IEEE
Date: 06-2016
Location: United States of America
Location: United States of America
Start Date: 12-2021
End Date: 12-2024
Amount: $425,948.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2023
End Date: 12-2023
Amount: $970,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2021
End Date: 06-2024
Amount: $403,882.00
Funder: Australian Research Council
View Funded Activity