ORCID Profile
0000-0001-8394-2391
Current Organisation
UNSW Sydney
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Publisher: IEEE
Date: 06-2017
Publisher: American Chemical Society (ACS)
Date: 12-12-2019
DOI: 10.1021/ACS.JPCLETT.9B03210
Abstract: The dynamics of photogenerated carriers and mobile ions in operational cesium lead halide (CsPbI
Publisher: IOP Publishing
Date: 13-06-2018
Publisher: AIP Publishing
Date: 07-01-2019
DOI: 10.1063/1.5081805
Abstract: Lead halide perovskite nanocrystals (NCs) have rapidly emerged as promising materials for low-cost and high-efficiency photovoltaic, optoelectronic, and photonic devices. The Stokes shift is a crucial parameter affecting their performance. In this work, we find that the external Stokes shift is strongly dependent on photon recycling. Due to the nonlinear nature of the quantum confinement effect (QCE), the bandgap distribution becomes extremely broad when the sizes are ultra-small, resulting in many repetitions of photon recycling and substantial emission redshift. Thereby, the smaller NCs exhibit larger external Stokes shifts. In detail, for the small NCs with the most probable size of 6.4 nm, the intrinsic Stokes shift is about 71 meV, but the observed external Stokes shift becomes 143.4 meV in the concentrated solution, whereas the intrinsic and apparent Stokes shifts are 69 and 97.6 meV for large NCs of 9.7 nm. Therefore, photon recycling significantly contributes to the external Stokes shift of perovskite NCs, in particular for the ultra-small sizes with strong QCE. This finding will add to the growing fundamental physical understanding of perovskites, which is of great interest due to their applications in photovoltaics and other fields.
Publisher: American Chemical Society (ACS)
Date: 28-07-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TC01656C
Abstract: Different dynamics of excitons and free carriers in 2D Ruddlesden–Popper halide perovskites with layer numbers of n = 1 and n ≥ 2.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR04787E
Abstract: The green fluorescence of CsPbBr 3 –Cs 4 PbBr 6 perovskite composites is ascribed to the emissions of band-edge and the defect trapped exciton of CsPbBr 3 .
Publisher: Springer Science and Business Media LLC
Date: 02-11-2018
DOI: 10.1038/S41467-018-07099-9
Abstract: Perovskite solar cells (PSCs) have reached an impressive efficiency over 23%. One of its promising characteristics is the low-cost solution printability, especially for flexible solar cells. However, printing large area uniform electron transport layers on rough and soft plastic substrates without hysteresis is still a great challenge. Herein, we demonstrate slot-die printed high quality tin oxide films for high efficiency flexible PSCs. The inherent hysteresis induced by the tin oxide layer is suppressed using a universal potassium interfacial passivation strategy regardless of fabricating methods. Results show that the potassium cations, not the anions, facilitate the growth of perovskite grains, passivate the interface, and contribute to the enhanced efficiency and stability. The small size flexible PSCs achieve a high efficiency of 17.18% and large size (5 × 6 cm 2 ) flexible modules obtain an efficiency over 15%. This passivation strategy has shown great promise for pursuing high performance large area flexible PSCs.
Publisher: Research Square Platform LLC
Date: 16-06-2021
DOI: 10.21203/RS.3.RS-629456/V1
Abstract: Super long perovskite microwires (PMWs) are in a great demand in many fields such as low-loss microcables and integrated optical waveguide. Despite decades of research into PMWs, single crystal PMWs with several centimeters long have not been obtained. Here, ultralong (up to 7.6 centimeters) monoclinic crystal structure CH3NH3PbI3·DMF PMWs have been synthesized. The high-quality microwire exhibits long carrier lifetime of 1775.7 ns. The as-prepared free-standing PMWs can be integrated to any arbitrary substrate and 808 nm near-infrared photodetectors have been successfully demonstrated. The fabricated device shows a high light on/off ratio of 1.79×106 and an extremely low dark current of 2.5 fA at 1 V bias. This work provides a strategy for the solution growth of ultralong microwires.
Publisher: Wiley
Date: 16-10-2017
Publisher: IEEE
Date: 06-2018
Publisher: American Chemical Society (ACS)
Date: 27-10-2022
Publisher: American Chemical Society (ACS)
Date: 30-06-2020
Publisher: American Chemical Society (ACS)
Date: 13-05-2020
Publisher: Walter de Gruyter GmbH
Date: 06-2020
Abstract: Lead (Pb) halide perovskites have witnessed highly promising achievements for high-efficiency solar cells, light-emitting diodes (LEDs), and photo/radiation detectors due to their exceptional optoelectronic properties. However, compound stability and Pb toxicity are still two main obstacles towards the commercialization of halide perovskite-based devices. Therefore, it is of substantial interest to search for non-toxic candidates with comparable photophysical characteristics. Metal-halide double perovskites (MHDPs), A 2 BBʹX 6 , are recently booming as promising alternatives for Pb-based halide-perovskites for their non-toxicity and significantly enhanced chemical and thermodynamic stability. Moreover, this family exhibits rich combinatorial chemistry with tuneable optoelectronic properties and thus a great potential for a broad range of optoelectronic/electronic applications. Herein, we present a comprehensive review of the MHDPs synthesized so far, and classified by their optical and electronic properties. We systematically generalize their electronic structure by both theoretical and experimental efforts to prospect the relevant optoelectronic properties required by different applications. The progress of the materials in various applications is explicated in view of the material structure-function relationship. Finally, a perspective outlook to improve the physical and optoelectronic properties of the materials is proposed aiming at fostering their future development and applications.
Publisher: American Chemical Society (ACS)
Date: 02-03-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TA00036E
Abstract: A strategy to utilize carbon dots for simultaneously improving photovoltaic performance and longevity of metal halide perovskite solar cells.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7NR07567G
Abstract: Photoexcited carriers are mainly excitons in InGaN/GaN multiple quantum well planar layers while free electron holes are greatly increased in nanorods.
Publisher: SPIE
Date: 22-12-2015
DOI: 10.1117/12.2202420
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0TC05676F
Abstract: A 2D Ga 2 S 3 enabled all-optical switch is realized upon a silicon-based on-chip platform. With the unique optical properties of the 2D nanoflakes, the device exhibits excellent switching behaviors driven by visible light at a low power density.
Publisher: Elsevier BV
Date: 04-2018
Publisher: Wiley
Date: 30-04-2019
Publisher: American Chemical Society (ACS)
Date: 06-08-2018
DOI: 10.1021/ACS.JPCLETT.8B02127
Abstract: Doping in perovskite is challenging and competitive due to the inherently fast growth mechanism of perovskite structure. Here, we demonstrate successful synthesis of high-yield Fe-doped cesium lead halide perovskite ultralong microwires (MWs) that have diameters up to ∼5 μm and lengths up to millimeters via an antisolvent vapor-assisted template-free method. Microstructure characterization confirms the uniformly doped Fe in the high-quality crystal perovskite MWs. Significantly, doping the Fe(III) concentration can affect both the MW morphology and photoluminescence (PL). The band edge emission of the MW at variable excitation has been accounted for by the superposition and combination of optical transitions of nearby singlet, triplet, and magnetic polaronic excitons. High-quality two-photon PL emission and the enhanced nonlinear absorption coefficient of Fe-doped MWs have been experimentally demonstrated. This superhigh nonlinear absorption coefficient and high-quality optical properties endow it with promising applications in spin-related optical switching and optical limiting devices.
Publisher: American Chemical Society (ACS)
Date: 15-10-2019
Publisher: American Chemical Society (ACS)
Date: 20-01-2021
Publisher: American Chemical Society (ACS)
Date: 07-2019
Abstract: Lead halide perovskites are widely applied in not only photovoltaics but also on-chip light sources and photon detection. To promote the incorporation of perovskite into integrated devices, microscale color patterning flexibility is a very important step. Here, we demonstrate spatially resolved modulation of the fluorescence of nanoplatelets (NPs) by femtosecond direct laser writing (fs-DLW). As the perovskite NP for the fs-DLW pattern is specially designed with a gradual bromide-iodide composition along the depth, the replacement of iodide ions by bromide ions can be activated under a controlled laser pulse and fluorescence is thus modulated from red to green. The effect of processing depth and NP thickness on fluorescence modulation is systemically investigated. The as-grown thick NP (thickness ≈ 500 nm) mainly exhibits a 690 nm emission from the bottom iodine-rich phase. After halide substitution induced by fs-DLW, a new fluorescence peak appears in the wavelength range of 540-600 nm the peak position and intensity are controlled by the DLW conditions. The fluorescent color is spatially modulated from red to green, enabling microscale-resolved multicolor emission. Compared with other currently available techniques, microscale color patterning via fs-DLW is a straightforward mask-free one-step operation, yielding high spatial resolution and enabling three-dimensional patterning by the multiple-photon method. We demonstrate that arbitrary patterns can be drawn on a wide range of perovskite NPs, implying the potential applications in microencryption, sensors, multicolor displays, lasers, and light-emitting devices.
Publisher: Wiley
Date: 23-05-2019
Publisher: Wiley
Date: 06-2019
Publisher: Wiley
Date: 04-2019
Publisher: American Chemical Society (ACS)
Date: 14-01-2020
Abstract: Metal and metal-oxide particles are commonly photodeposited on photocatalysts by reduction and oxidation reactions, respectively, consuming charges that are generated under illumination. This study reveals that amorphous MoO
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8TC03599G
Abstract: The antimony-doped tin oxide buffer layer greatly improve the extraction of carriers in a PbSe QD solar cell.
Publisher: Elsevier BV
Date: 05-2004
Publisher: SPIE
Date: 23-02-2017
DOI: 10.1117/12.2251197
Publisher: American Chemical Society (ACS)
Date: 12-09-2019
DOI: 10.1021/ACS.JPCLETT.9B02423
Abstract: Colloidal quantum dot solids are attractive candidates for tandem solar cells because of their widely tunable bandgaps. However, the development of the quantum dot tandem solar cell has lagged far behind that of its single-junction counterpart. One of the fundamental problems with colloidal quantum dot solar cells is the relatively small diffusion length, which limits the quantum dot absorbing layer thickness and hence the power conversion efficiency. In this research, guided by optical modeling and utilizing a graded band alignment strategy, a two-terminal monolithic solution-processed quantum dot tandem solar cell has been successfully fabricated and a power conversion efficiency of 6.8% has been achieved. The band grading approach utilized the complementary tuning of work functions and band alignment through judicious choices of the nanoparticle surface chemistry and quantum dot confined size. This work demonstrates a general approach to improving the efficiency for tandem thin-film solar cells.
Publisher: MDPI AG
Date: 19-02-2023
DOI: 10.3390/JCM12041651
Abstract: Hip displacement is the second most common musculoskeletal deformity in children with cerebral palsy. Hip surveillance programs have been implemented in many countries to detect hip displacement early when it is usually asymptomatic. The aim of hip surveillance is to monitor hip development to offer management options to slow or reverse hip displacement, and to provide the best opportunity for good hip health at skeletal maturity. The long-term goal is to avoid the sequelae of late hip dislocation which may include pain, fixed deformity, loss of function and impaired quality of life. The focus of this review is on areas of disagreement, areas where evidence is lacking, ethical dilemmas and areas for future research. There is already broad agreement on how to conduct hip surveillance, using a combination of standardised physical examination measures and radiographic examination of the hips. The frequency is dictated by the risk of hip displacement according to the child’s ambulatory status. Management of both early and late hip displacement is more controversial and the evidence base in key areas is relatively weak. In this review, we summarise the recent literature on hip surveillance and highlight the management dilemmas and controversies. Better understanding of the causes of hip displacement may lead to interventions which target the pathophysiology of hip displacement and the pathological anatomy of the hip in children with cerebral palsy. We have identified the need for more effective and integrated management from early childhood to skeletal maturity. Areas for future research are highlighted and a range of ethical and management dilemmas are discussed.
Publisher: Springer Science and Business Media LLC
Date: 14-06-2021
Publisher: Wiley
Date: 20-08-2019
Publisher: American Chemical Society (ACS)
Date: 04-2021
Publisher: American Chemical Society (ACS)
Date: 28-08-2018
Abstract: The current-voltage hysteresis, as well as the performance instability of perovskite solar cells (PSCs) under a working condition, is serving as the major obstacle toward their commercialization while the exact fundamental mechanisms to these issues are still in debate. In this study, we investigated the slow variation of photogenerated carrier dynamics in a (FAPbI
Publisher: IOP Publishing
Date: 23-12-2016
DOI: 10.1088/1361-6528/28/5/055201
Abstract: Nanotextured surfaces provide an ideal platform for efficiently capturing and emitting light. However, the increased surface area in combination with surface defects induced by nanostructuring e.g. using reactive ion etching (RIE) negatively affects the device's active region and, thus, drastically decreases device performance. In this work, the influence of structural defects and surface states on the optical and electrical performance of InGaN/GaN nanorod (NR) light emitting diodes (LEDs) fabricated by top-down RIE of c-plane GaN with InGaN quantum wells was investigated. After proper surface treatment a significantly improved device performance could be shown. Therefore, wet chemical removal of damaged material in KOH solution followed by atomic layer deposition of only 10 [Formula: see text] alumina as wide bandgap oxide for passivation were successfully applied. Raman spectroscopy revealed that the initially compressively strained InGaN/GaN LED layer stack turned into a virtually completely relaxed GaN and partially relaxed InGaN combination after RIE etching of NRs. Time-correlated single photon counting provides evidence that both treatments-chemical etching and alumina deposition-reduce the number of pathways for non-radiative recombination. Steady-state photoluminescence revealed that the luminescent performance of the NR LEDs is increased by about 50% after KOH and 80% after additional alumina passivation. Finally, complete NR LED devices with a suspended graphene contact were fabricated, for which the effectiveness of the alumina passivation was successfully demonstrated by electroluminescence measurements.
Publisher: Elsevier BV
Date: 08-2018
Publisher: Wiley
Date: 11-10-2020
Publisher: American Chemical Society (ACS)
Date: 27-08-2018
Publisher: SPIE
Date: 02-01-2017
DOI: 10.1117/12.2283328
Publisher: Optica Publishing Group
Date: 30-10-2020
DOI: 10.1364/PRJ.402411
Abstract: Halide perovskites, such as methylammonium lead halide perovskites ( MAPbX 3 , X = I , Br, and Cl), are emerging as promising candidates for a wide range of optoelectronic applications, including solar cells, light-emitting diodes, and photodetectors, due to their superior optoelectronic properties. All-inorganic lead halide perovskites CsPbX 3 are attracting a lot of attention because replacing the organic cations with Cs + enhances the stability, and its halide-mixing derivatives offer broad bandgap tunability covering nearly the entire visible spectrum. However, there is evidence suggesting that the optical properties of mixed-halide perovskites are influenced by phase segregation under external stimuli, especially illumination, which may negatively impact the performance of optoelectronic devices. It is reported that the mixed-halide perovskites in forms of thin films and nanocrystals are segregated into a low-bandgap I-rich phase and a high-bandgap Br-rich phase. Herein, we present a critical review on the synthesis and basic properties of all-inorganic perovskites, phase-segregation phenomena, plausible mechanisms, and methods to mitigate phase segregation, providing insights on advancing mixed-halide perovskite optoelectronics with reliable performance.
Publisher: Elsevier BV
Date: 05-2003
Publisher: SPIE
Date: 16-02-2017
DOI: 10.1117/12.2249931
Publisher: Wiley
Date: 18-09-0044
Abstract: Colloidal quantum dots (QDs) are promising candidate materials for photovoltaics (PV) owing to the tunable bandgap and low-cost solution processability. Lead selenide (PbSe) QDs are particularly attractive to PV applications due to the efficient multiple-exciton generation and carrier transportation. However, surface defects arising from the oxidation of the PbSe QDs have been the major limitation for their development in PV. Here, a new passivation method for chlorinated PbSe QDs via ion exchange with cesium lead halide (Br, I) perovskite nanocrystals is reported. The surface chloride ions on the as-synthesized QDs can be partially exchanged with bromide or iodide ions from the perovskite nanocrystals, hence forming a hybrid halide passivation. Consistent with the improved photoluminescence quantum yield, the ch ion PV device fabricated with these PbSe QDs achieves a PCE of 8.2%, compared to 7.3% of that fabricated with the untreated QDs. This new method also leads to devices with excellent air-stability, retaining at least 93% of their initial PCEs after being stored in ambient conditions for 57 d. This is considered as the first reported PbSe QD solar cell with a PCE of over 8% to date.
Publisher: IOP Publishing
Date: 25-04-2019
Abstract: Cs
Publisher: Elsevier BV
Date: 09-2020
No related grants have been discovered for Weijian Chen.