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Dr. Mingqing Wang
UCL Institute for Materials Discovery University College of London, Room 107, Roberts Building, Malet Place, London WC1E 7JE United Kingdom

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0 light emitting diodes
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0 photodetectors
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light emitting diodes
Perovskite quantum dots
photodetectors

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Research article
Published: 28 July 2021 in ACS Applied Materials & Interfaces
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A new process to crystallize amorphous silicon without melting and the generation of excessive heating of nearby components is presented. We propose the addition of a molybdenum layer to improve the quality of the laser-induced crystallization over that achieved by direct irradiation of silicon alone. The advantages are that it allows the control of crystallite size by varying the applied fluence of a near-infrared femtosecond laser. It offers two fluence regimes for nanocrystallization and polycrystallization with small and large crystallite sizes, respectively. The high repetition rate of the compact femtosecond laser source enables high-quality crystallization over large areas. In this proposed method, a multilayer structure is irradiated with a single femtosecond laser pulse. The multilayer structure includes a substrate, a target amorphous Si layer coated with an additional molybdenum thin film. The Si layer is crystallized by irradiating the Mo layer at different fluence regimes. The transfer of energy from the irradiated Mo layer to the Si film causes the crystallization of amorphous Si at low temperatures (∼700 K). Numerical simulations were carried out to estimate the electron and lattice temperatures for different fluence regimes using a two-temperature model. The roles of direct phonon transport and inelastic electron scattering at the Mo–Si interface were considered in the transfer of energy from the Mo to the Si film. The simulations confirm the experimental evidence that amorphous Si was crystallized in an all-solid-state process at temperatures lower than the melting point of Si, which is consistent with the results from transmission electron microscopy (TEM) and Raman. The formation of crystallized Si with controlled crystallite size after laser treatment can lead to longer mean free paths for carriers and increased electrical conductivity.

ACS Style

Nazar Farid; Adam Brunton; Phil Rumsby; Scott Monaghan; Ray Duffy; Paul Hurley; Mingqing Wang; Kwang-Leong Choy; Gerard M. O’Connor. Femtosecond Laser-Induced Crystallization of Amorphous Silicon Thin Films under a Thin Molybdenum Layer. ACS Applied Materials & Interfaces 2021, 13, 37797 -37808.

AMA Style

Nazar Farid, Adam Brunton, Phil Rumsby, Scott Monaghan, Ray Duffy, Paul Hurley, Mingqing Wang, Kwang-Leong Choy, Gerard M. O’Connor. Femtosecond Laser-Induced Crystallization of Amorphous Silicon Thin Films under a Thin Molybdenum Layer. ACS Applied Materials & Interfaces. 2021; 13 (31):37797-37808.

Chicago/Turabian Style

Nazar Farid; Adam Brunton; Phil Rumsby; Scott Monaghan; Ray Duffy; Paul Hurley; Mingqing Wang; Kwang-Leong Choy; Gerard M. O’Connor. 2021. "Femtosecond Laser-Induced Crystallization of Amorphous Silicon Thin Films under a Thin Molybdenum Layer." ACS Applied Materials & Interfaces 13, no. 31: 37797-37808.

Journal article
Published: 20 July 2021 in Physica B: Condensed Matter
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Hole transport material (HTM) is a major component of perovskite solar cells (PSCs). PEDOT: PSS, an organic HTM, is widely used in inverted (p-i-n) PSCs. While PEDOT: PSS is unstable, expensive and it's acidic nature could deteriorate the absorber. Copper zinc tin sulphide (CZTS), an inorganic semiconductor can be used as HTM due to its properties such as low cost, ease of synthesis and high hole mobility. In this work, device simulation of inverted (p-i-n) PSC was performed with CZTS as HTM to exploit its maximum capability. Remarkable power conversion efficiency (PCE) of 25.43% was achieved after optimizing the performance. Device performance was strongly affected by thickness and electron affinity of HTM as well as diffusion length of carriers. PCE of real fabricated device was also found to be 9.72%. This work demonstrates CZTS is a promising candidate to replace PEDOT: PSS from both experimental and theoretical perspectives.

ACS Style

Syed Zulqarnain Haider; Hafeez Anwar; Mingqing Wang. Remarkable performance optimization of inverted p-i-n architecture perovskite solar cell with CZTS as hole transport material. Physica B: Condensed Matter 2021, 620, 413270 .

AMA Style

Syed Zulqarnain Haider, Hafeez Anwar, Mingqing Wang. Remarkable performance optimization of inverted p-i-n architecture perovskite solar cell with CZTS as hole transport material. Physica B: Condensed Matter. 2021; 620 ():413270.

Chicago/Turabian Style

Syed Zulqarnain Haider; Hafeez Anwar; Mingqing Wang. 2021. "Remarkable performance optimization of inverted p-i-n architecture perovskite solar cell with CZTS as hole transport material." Physica B: Condensed Matter 620, no. : 413270.

Journal article
Published: 23 June 2021 in ACS Applied Materials & Interfaces
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Narrow-band-gap III–V semiconductor nanowires (NWs) with a suitable band structure and strong light-trapping ability are ideal for high-efficiency low-cost solar water-splitting systems. However, due to their nanoscale dimension, they suffer more severe corrosion by the electrolyte solution than the thin-film counterparts. Thus, short-term durability is the major obstacle for using these NWs for practical water-splitting applications. Here, we demonstrated for the first time that a thin layer (∼7 nm thick) of compact TiO2 deposited by atomic layer deposition can provide robust protection to III–V NWs. The protected GaAs NWs maintain 91.4% of its photoluminescence intensity after 14 months of storage in ambient atmosphere, which suggests the TiO2 layer is pinhole-free. Working as a photocathode for water splitting, they exhibited a 45% larger photocurrent density compared with unprotected counterparts and a high Faraday efficiency of 91% and can also maintain a record-long highly stable performance among narrow-band-gap III–V NW photoelectrodes; after 67 h photoelectrochemical stability test reaction in a strong acid electrolyte solution (pH = 1), they show no apparent indication of corrosion, which is in stark contrast to the unprotected NWs that fully failed after 35 h. These findings provide an effective way to enhance both stability and performance of III–V NW-based photoelectrodes, which are highly important for practical applications in solar-energy-based water-splitting systems.

ACS Style

Fan Cui; Yunyan Zhang; H. Aruni Fonseka; Premrudee Promdet; Ali Imran Channa; Mingqing Wang; Xueming Xia; Sanjayan Sathasivam; Hezhuang Liu; Ivan P. Parkin; Hui Yang; Ting Li; Kwang-Leong Choy; Jiang Wu; Christopher Blackman; Ana M. Sanchez; Huiyun Liu. Robust Protection of III–V Nanowires in Water Splitting by a Thin Compact TiO2 Layer. ACS Applied Materials & Interfaces 2021, 13, 30950 -30958.

AMA Style

Fan Cui, Yunyan Zhang, H. Aruni Fonseka, Premrudee Promdet, Ali Imran Channa, Mingqing Wang, Xueming Xia, Sanjayan Sathasivam, Hezhuang Liu, Ivan P. Parkin, Hui Yang, Ting Li, Kwang-Leong Choy, Jiang Wu, Christopher Blackman, Ana M. Sanchez, Huiyun Liu. Robust Protection of III–V Nanowires in Water Splitting by a Thin Compact TiO2 Layer. ACS Applied Materials & Interfaces. 2021; 13 (26):30950-30958.

Chicago/Turabian Style

Fan Cui; Yunyan Zhang; H. Aruni Fonseka; Premrudee Promdet; Ali Imran Channa; Mingqing Wang; Xueming Xia; Sanjayan Sathasivam; Hezhuang Liu; Ivan P. Parkin; Hui Yang; Ting Li; Kwang-Leong Choy; Jiang Wu; Christopher Blackman; Ana M. Sanchez; Huiyun Liu. 2021. "Robust Protection of III–V Nanowires in Water Splitting by a Thin Compact TiO2 Layer." ACS Applied Materials & Interfaces 13, no. 26: 30950-30958.

Journal article
Published: 21 July 2020 in Current Applied Physics
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Inverted perovskite solar cells (p-i-n PSCs) have been fascinated due to rapid progress of performance in recent years. PEDOT:PSS is commonly used hole transport material (HTM) in p-i-n PSCs having hygroscopic and acidic nature that leads towards poor performance of device. Therefore, it is necessary to replace PEDOT:PSS with stable HTM. In this paper, theoretical study is carried out to investigate physical parameters that can affect the performance of p-i-n PSCs with copper iodide (CuI) as HTM. These parameters include the effect of doping density of electron transport material (ETM), absorber and HTM as well as defect density and thickness of absorber on the performance of p-i-n PSCs. Hole mobility and thickness of HTM are also investigated. It is found that performance of p-i-n PSCs is strongly dependent on defect density and thickness of absorber. Upon final optimization, device attains PCE of more than 21% which is encouraging.

ACS Style

Syed Zulqarnain Haider; Hafeez Anwar; Sehrish Manzoor; Ahmad G. Ismail; Mingqing Wang. A theoretical study for high-performance inverted p-i-n architecture perovskite solar cells with cuprous iodide as hole transport material. Current Applied Physics 2020, 20, 1080 -1089.

AMA Style

Syed Zulqarnain Haider, Hafeez Anwar, Sehrish Manzoor, Ahmad G. Ismail, Mingqing Wang. A theoretical study for high-performance inverted p-i-n architecture perovskite solar cells with cuprous iodide as hole transport material. Current Applied Physics. 2020; 20 (9):1080-1089.

Chicago/Turabian Style

Syed Zulqarnain Haider; Hafeez Anwar; Sehrish Manzoor; Ahmad G. Ismail; Mingqing Wang. 2020. "A theoretical study for high-performance inverted p-i-n architecture perovskite solar cells with cuprous iodide as hole transport material." Current Applied Physics 20, no. 9: 1080-1089.

Review
Published: 24 June 2020 in Sustainability
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Kesterite Cu2ZnSnS4 (CZTS) has attracted attention as an earth-abundant alternative to commercially successful CIGS solar cells. CZTS exhibits decent optoelectrical properties while having excellent stability on top of being an earth-abundant, low-cost and non-toxic material. Therefore, in recent years, there has been a significant research effort to develop CZTS-based devices. The efficiency of CZTS solar cells reached 12.6% in 2013, and this was a remarkable achievement at the time. However, the efficiency of these devices has been stagnant since then while emerging technologies, most notably perovskite solar cells, keep breaking record after record. Currently, CZTS research focuses on discovering the secrets of material properties that hinder the efficiency of CZTS solar cells while branching out to develop alternative applications for this material. In this review, we summarize the interesting properties of CZTS as well as its promising applications, which include thin-film solar cells, charge-transfer layers in perovskite solar cells, and photoelectrochemical water splitting while briefly commenting on its other possible applications.

ACS Style

Ahmet Nazligul; Mingqing Wang; Kwang Choy. Recent Development in Earth-Abundant Kesterite Materials and Their Applications. Sustainability 2020, 12, 5138 .

AMA Style

Ahmet Nazligul, Mingqing Wang, Kwang Choy. Recent Development in Earth-Abundant Kesterite Materials and Their Applications. Sustainability. 2020; 12 (12):5138.

Chicago/Turabian Style

Ahmet Nazligul; Mingqing Wang; Kwang Choy. 2020. "Recent Development in Earth-Abundant Kesterite Materials and Their Applications." Sustainability 12, no. 12: 5138.

Communication
Published: 21 April 2020 in Advanced Materials
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Flexible devices are garnering substantial interest owing to their potential for wearable and portable applications. Here, flexible and self‐powered photodetector arrays based on all‐inorganic perovskite quantum dots (QDs) are reported. CsBr/KBr‐mediated CsPbBr3 QDs possess improved surface morphology and crystallinity with reduced defect densities, in comparison with the pristine ones. Systematic material characterizations reveal enhanced carrier transport, photoluminescence efficiency, and carrier lifetime of the CsBr/KBr‐mediated CsPbBr3 QDs. Flexible photodetector arrays fabricated with an optimum CsBr/KBr treatment demonstrate a high open‐circuit voltage of 1.3 V, responsivity of 10.1 A W−1, specific detectivity of 9.35 × 1013 Jones, and on/off ratio up to ≈104. Particularly, such performance is achieved under the self‐powered operation mode. Furthermore, outstanding flexibility and electrical stability with negligible degradation after 1600 bending cycles (up to 60°) are demonstrated. More importantly, the flexible detector arrays exhibit uniform photoresponse distribution, which is of much significance for practical imaging systems, and thus promotes the practical deployment of perovskite products.

ACS Style

Kai Shen; Hao Xu; Xiao Li; Jian Guo; Sanjayan Sathasivam; Mingqing Wang; Aobo Ren; Kwang Leong Choy; Ivan P. Parkin; Zhengxiao Guo; Jiang Wu. Flexible and Self‐Powered Photodetector Arrays Based on All‐Inorganic CsPbBr 3 Quantum Dots. Advanced Materials 2020, 32, e2000004 .

AMA Style

Kai Shen, Hao Xu, Xiao Li, Jian Guo, Sanjayan Sathasivam, Mingqing Wang, Aobo Ren, Kwang Leong Choy, Ivan P. Parkin, Zhengxiao Guo, Jiang Wu. Flexible and Self‐Powered Photodetector Arrays Based on All‐Inorganic CsPbBr 3 Quantum Dots. Advanced Materials. 2020; 32 (22):e2000004.

Chicago/Turabian Style

Kai Shen; Hao Xu; Xiao Li; Jian Guo; Sanjayan Sathasivam; Mingqing Wang; Aobo Ren; Kwang Leong Choy; Ivan P. Parkin; Zhengxiao Guo; Jiang Wu. 2020. "Flexible and Self‐Powered Photodetector Arrays Based on All‐Inorganic CsPbBr 3 Quantum Dots." Advanced Materials 32, no. 22: e2000004.

Conference paper
Published: 01 October 2019 in 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)
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The materials used in detection of high energy photons are of primary importance in the construction of efficient, cost effective and sensitive detectors. Current research into Perovskites for solar cell technology has stimulated interest in their potential alternative uses, one of which is in direct photon conversion radiation detectors, owed primarily to their high-Z elemental composition twinned with exceptional charge carrier transport properties. Here, the Perovskite CsPbBr 3 has been synthesised through solution growth. The raw CsPbBr 3 was a granular powder which was formed into disks of 8 mm diameter and 1-2 mm thickness by two methods: 1). the powders were pressed into pellets using a hydraulic press or 2). sealed in a quartz ampoule under vacuum and then melted and quenched to form a polycrystalline solid which was cut to size. Metallic contacts were deposited on the front and back faces to permit charge collection. The results from the pressed devices are promising, particularly given that the production method is cost effective, repeatable and scalable. The solid-from-melt devices show similar performance but further development is required to optimise the production method.

ACS Style

Logan J. Forth; Mingqing Wang; Issy Braddock; Jia C. Khong; Rob Moss; Paul Sellin; Kwang L. Choy; Robert Speller. Sensitive X-ray Detectors Synthesised from CsPbBr3. 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) 2019, 1 -5.

AMA Style

Logan J. Forth, Mingqing Wang, Issy Braddock, Jia C. Khong, Rob Moss, Paul Sellin, Kwang L. Choy, Robert Speller. Sensitive X-ray Detectors Synthesised from CsPbBr3. 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). 2019; ():1-5.

Chicago/Turabian Style

Logan J. Forth; Mingqing Wang; Issy Braddock; Jia C. Khong; Rob Moss; Paul Sellin; Kwang L. Choy; Robert Speller. 2019. "Sensitive X-ray Detectors Synthesised from CsPbBr3." 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) , no. : 1-5.

Journal article
Published: 24 September 2019 in Molecules
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Perovskite solar cells (PSCs) have achieved tremendous success within just a decade. This success is critically dependent upon compositional engineering, morphology control of perovskite layer, or contingent upon high-temperature annealed mesoporous TiO2, but quantitative analysis of the role of facile TiCl4 treatment and thickness control of the compact TiO2 layer has not been satisfactorily undertaken. Herein, we report the facile thickness control and post-treatment of the electron transport TiO2 layer to produce highly efficient planar PSCs. TiCl4 treatment of TiO2 layer could remove the surface trap and decrease the charge recombination in the prepared solar cells. Introduction of ethanol into the TiCl4 aqueous solution led to further improved open-circuit voltage and short-circuit current density of the related devices, thus giving rise to enhanced power conversion efficiency (PCE). After the optimal TiCl4 treatment, PCE of 16.42% was achieved for PSCs with TiCl4 aqueous solution-treated TiO2 and 19.24% for PSCs with TiCl4 aqueous/ethanol solution-treated TiO2, respectively. This work sheds light on the promising potential of simple planar PSCs without complicated compositional engineering and avoiding the deposition and optimization of the mesoporous scaffold layer.

ACS Style

Weifu Sun; Kwang-Leong Choy; Mingqing Wang. The Role of Thickness Control and Interface Modification in Assembling Efficient Planar Perovskite Solar Cells. Molecules 2019, 24, 3466 .

AMA Style

Weifu Sun, Kwang-Leong Choy, Mingqing Wang. The Role of Thickness Control and Interface Modification in Assembling Efficient Planar Perovskite Solar Cells. Molecules. 2019; 24 (19):3466.

Chicago/Turabian Style

Weifu Sun; Kwang-Leong Choy; Mingqing Wang. 2019. "The Role of Thickness Control and Interface Modification in Assembling Efficient Planar Perovskite Solar Cells." Molecules 24, no. 19: 3466.

Original paper
Published: 04 April 2019 in physica status solidi (a)
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Recently, perovskite solar cells (PSCs) have achieved remarkable power conversion efficiency (PCE) about 22.6%. While most of the hole transport materials (HTMs) used in PSCs are organic in nature with an issue of instability and high cost. In this paper, copper thiocyanate (CuSCN), a low cost inorganic HTM with excellent thermal and moisture stability, is applied as HTM for perovskite solar cells. The device modeling of PSCs is based on the device structure of FTO/TiO2/MAPbI3/CuSCN/Au. Two interface defect layers, IDL1 as electron transport material (ETM)/absorber interface and IDL2 as absorber/HTM interface, are introduced into the device model in order to study the impact of interface quality on the performance of PSCs. Among all of the parameters, defect density and conduction band offset (CBO) at ETM/absorber interface together with the defect density of absorber influence the device performance appreciably. Upon optimization of all of the parameters, PCE of the device approaches to 25.02%, which is very encouraging. The result shows that lead‐based PSC with CuSCN as HTM is an efficient system due to its enhanced hole transport, high electric conductivity, and improved chemical interaction with absorber. Further, defect density of ETM/absorber interface and absorber layer could be reduced by optimized deposition process.

ACS Style

Syed Zulqarnain Haider; Hafeez Anwar; Mingqing Wang. Theoretical Device Engineering for High‐Performance Perovskite Solar Cells Using CuSCN as Hole Transport Material Boost the Efficiency Above 25%. physica status solidi (a) 2019, 216, 1 .

AMA Style

Syed Zulqarnain Haider, Hafeez Anwar, Mingqing Wang. Theoretical Device Engineering for High‐Performance Perovskite Solar Cells Using CuSCN as Hole Transport Material Boost the Efficiency Above 25%. physica status solidi (a). 2019; 216 (11):1.

Chicago/Turabian Style

Syed Zulqarnain Haider; Hafeez Anwar; Mingqing Wang. 2019. "Theoretical Device Engineering for High‐Performance Perovskite Solar Cells Using CuSCN as Hole Transport Material Boost the Efficiency Above 25%." physica status solidi (a) 216, no. 11: 1.

Journals
Published: 25 February 2019 in Journal of Materials Chemistry A
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ZnO nanoparticle decorated all-inorganic perovskite quantum dots exhibit improved photoresponse and long-term stability.

ACS Style

Kai Shen; Xiao Li; Hao Xu; Mingqing Wang; Xiao Dai; Jian Guo; Ting Zhang; Shibin Li; Guifu Zou; Kwang-Leong Choy; Ivan P. Parkin; Zhengxiao Guo; Huiyun Liu; Jiang Wu. Enhanced performance of ZnO nanoparticle decorated all-inorganic CsPbBr3 quantum dot photodetectors. Journal of Materials Chemistry A 2019, 7, 6134 -6142.

AMA Style

Kai Shen, Xiao Li, Hao Xu, Mingqing Wang, Xiao Dai, Jian Guo, Ting Zhang, Shibin Li, Guifu Zou, Kwang-Leong Choy, Ivan P. Parkin, Zhengxiao Guo, Huiyun Liu, Jiang Wu. Enhanced performance of ZnO nanoparticle decorated all-inorganic CsPbBr3 quantum dot photodetectors. Journal of Materials Chemistry A. 2019; 7 (11):6134-6142.

Chicago/Turabian Style

Kai Shen; Xiao Li; Hao Xu; Mingqing Wang; Xiao Dai; Jian Guo; Ting Zhang; Shibin Li; Guifu Zou; Kwang-Leong Choy; Ivan P. Parkin; Zhengxiao Guo; Huiyun Liu; Jiang Wu. 2019. "Enhanced performance of ZnO nanoparticle decorated all-inorganic CsPbBr3 quantum dot photodetectors." Journal of Materials Chemistry A 7, no. 11: 6134-6142.

Communication
Published: 31 January 2019 in Chemical Communications
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A CIGS-based photocathode combined with an earth abundant Co–S catalyst has demonstrated remarkable photoelectrochemical hydrogen generation in neutral electrolyte.

ACS Style

Mingqing Wang; Yung-Shan Chang; Chun-Wen Tsao; Mei-Jing Fang; Yung-Jung Hsu; Kwang-Leong Choy. Enhanced photoelectrochemical hydrogen generation in neutral electrolyte using non-vacuum processed CIGS photocathodes with an earth-abundant cobalt sulfide catalyst. Chemical Communications 2019, 55, 2465 -2468.

AMA Style

Mingqing Wang, Yung-Shan Chang, Chun-Wen Tsao, Mei-Jing Fang, Yung-Jung Hsu, Kwang-Leong Choy. Enhanced photoelectrochemical hydrogen generation in neutral electrolyte using non-vacuum processed CIGS photocathodes with an earth-abundant cobalt sulfide catalyst. Chemical Communications. 2019; 55 (17):2465-2468.

Chicago/Turabian Style

Mingqing Wang; Yung-Shan Chang; Chun-Wen Tsao; Mei-Jing Fang; Yung-Jung Hsu; Kwang-Leong Choy. 2019. "Enhanced photoelectrochemical hydrogen generation in neutral electrolyte using non-vacuum processed CIGS photocathodes with an earth-abundant cobalt sulfide catalyst." Chemical Communications 55, no. 17: 2465-2468.

Accepted manuscript
Published: 05 January 2018 in Semiconductor Science and Technology
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Hole transport material (HTM) plays an important role in the efficiency and stability of perovskite solar cells (PSCs). Spiro-MeOTAD, the commonly used HTM, is costly and can be easily degraded by heat and moisture, thus offering hindrance to commercialize PSCs. There is dire need to find an alternate inorganic and stable HTM to exploit PSCs with their maximum capability. In this paper, a comprehensive device simulation is used to study various possible parameters that can influence the performance of perovskite solar cell with CuI as HTM. These include the effect of doping density, defect density and thickness of absorber layer, along with the influence of diffusion length of carriers as well as electron affinity of electron transport layer (ETM) and HTM on the performance of perovskite solar cells. In addition, hole mobility and doping density of HTM is also investigated. CuI is a p-type inorganic material with low cost and relatively high stability. It is found that concentration of dopant in absorber layer and HTM, the electron affinity of HTM and ETM affect the performance of solar cell minutely, while cell performance improves greatly with the reduction of defect density. Upon optimization of parameters, power conversion efficiency (PCE) for this device is found to be 21.32%. The result shows that lead-based PSC with CuI as HTM is an efficient system. Enhancing the stability and reduction of defect density are critical factors for future research. These factors can be improved by better fabrication process and proper encapsulation of solar cell.

ACS Style

Syed Zulqarnain Haider; Hafeez Anwar; Mingqing Wang. A comprehensive device modelling of perovskite solar cell with inorganic copper iodide as hole transport material. Semiconductor Science and Technology 2018, 33, 035001 .

AMA Style

Syed Zulqarnain Haider, Hafeez Anwar, Mingqing Wang. A comprehensive device modelling of perovskite solar cell with inorganic copper iodide as hole transport material. Semiconductor Science and Technology. 2018; 33 (3):035001.

Chicago/Turabian Style

Syed Zulqarnain Haider; Hafeez Anwar; Mingqing Wang. 2018. "A comprehensive device modelling of perovskite solar cell with inorganic copper iodide as hole transport material." Semiconductor Science and Technology 33, no. 3: 035001.

Journal article
Published: 06 November 2017 in CrystEngComm
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Tuning the morphology, composition and photoluminescence emission over almost the entire visible region of all-inorganic cesium lead halide nanocrystals by a general and facile one-pot synthetic approach. This study demonstrates a facile and general one-pot synthetic approach for all-inorganic colloidal cesium lead halide (CsPbX 3 , X = Cl, Br, I, mixed Cl/Br, Br/I) perovskite nanocrystals (NCs) by directly heating the precursors/solvent/ligands. In contrast to typical routes, these reactions are conducted in open air, requiring neither high temperature dissolution nor a vacuum/inert atmosphere. The composition, shape and size of the as-synthesized NCs can be finely tuned by varying the reaction parameters such as temperature and time, ligand species and precursor halide ratios. CsPbX 3 morphologies may be varied from perovskite nanoplatelets (NPLs) to nanosheets and sphere-like NCs, each with tunable absorption spectra and photoluminescence (PL) emissions. In particular, mixed halide NCs with controllable band gaps and PL emission across the entire visible region have been demonstrated by tuning the precursor halide ratios. The reproducibility and scalability of the present synthetic protocol is elaborated by upscaling the amounts of chemicals and solvents/ligands in a representative synthesis of CsPbBr 3 NPLs. The representative large-scale CsPbBr 3 NPLs exhibit a high PL quantum yield of 73.56%.

ACS Style

Emmanuel Acheampong Tsiwah; Yanxi Ding; Zixiong Li; Zhiyong Zhao; Mingqing Wang; Chao Hu; Xiaoqing Liu; Chenghua Sun; Xiujian Zhao; Yi Xie. One-pot scalable synthesis of all-inorganic perovskite nanocrystals with tunable morphology, composition and photoluminescence. CrystEngComm 2017, 19, 7041 -7049.

AMA Style

Emmanuel Acheampong Tsiwah, Yanxi Ding, Zixiong Li, Zhiyong Zhao, Mingqing Wang, Chao Hu, Xiaoqing Liu, Chenghua Sun, Xiujian Zhao, Yi Xie. One-pot scalable synthesis of all-inorganic perovskite nanocrystals with tunable morphology, composition and photoluminescence. CrystEngComm. 2017; 19 (46):7041-7049.

Chicago/Turabian Style

Emmanuel Acheampong Tsiwah; Yanxi Ding; Zixiong Li; Zhiyong Zhao; Mingqing Wang; Chao Hu; Xiaoqing Liu; Chenghua Sun; Xiujian Zhao; Yi Xie. 2017. "One-pot scalable synthesis of all-inorganic perovskite nanocrystals with tunable morphology, composition and photoluminescence." CrystEngComm 19, no. 46: 7041-7049.

Journal article
Published: 28 July 2017 in Scientific Reports
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In our work, eco-friendly, non-vacuum and low cost Electrostatic Spray Assisted Vapour Deposition (ESAVD) method has been used to produce Cu(In,Ga)(S,Se)2 (CIGS) solar cells. Copper (Cu) deficient (Cu/In + Ga = 0.76) CIGS films were designed to avoid the rather dangerous KCN treatment step for the removal of conductive minor phases of Cu2S/Cu2Se. A simple sodium (Na) treatment method was used to modify the morphology and electronic properties of the absorber and it clearly improved the solar cell performance. The SEM and XRD results testified a slightly increase of the grain size and (112) crystal orientation in the Na-incorporated CIGS thin films. From the Mott-schottky results, it can be seen that the functions of the Na treatment in our non-vacuum deposited CIGS are mainly used for defect passivation and reduction of charge recombination. Photovoltaic characteristics and j-V curve demonstrated that the dipping of CIGS films in 0.2 M NaCl solution for 20 minutes followed by selenization at 550 °C under selenium vapor resulted in the optimum photovoltaic performance, with j sc, V oc, FF and η of the optimized solar cell of 29.30 mA cm−2, 0.564 V, 65.59% and 10.83%, respectively.

ACS Style

Mingqing Wang; Anower Hossain; Kwang-Leong Choy. Effect of Sodium Treatment on the Performance of Electrostatic Spray Assisted Vapour Deposited Copper-poor Cu(In,Ga)(S,Se) 2 Solar Cells. Scientific Reports 2017, 7, 1 -10.

AMA Style

Mingqing Wang, Anower Hossain, Kwang-Leong Choy. Effect of Sodium Treatment on the Performance of Electrostatic Spray Assisted Vapour Deposited Copper-poor Cu(In,Ga)(S,Se) 2 Solar Cells. Scientific Reports. 2017; 7 (1):1-10.

Chicago/Turabian Style

Mingqing Wang; Anower Hossain; Kwang-Leong Choy. 2017. "Effect of Sodium Treatment on the Performance of Electrostatic Spray Assisted Vapour Deposited Copper-poor Cu(In,Ga)(S,Se) 2 Solar Cells." Scientific Reports 7, no. 1: 1-10.

Journal article
Published: 22 February 2017 in CrystEngComm
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We report the gram-scale synthesis of Cu-poor CZTS nanocrystals (NCs) with tuned shapes and compositions by using a facile phosphine-free heat-up procedure. Based on the detailed characterization and analyses of the evolution of crystal phases, compositions, morphologies and optical spectra over the reaction stage and temperature, we explore the reaction mechanism. The synthesis reaction involves the formation of binary CuS (covellite) nanoparticles at room temperature, and the conversion from the as-formed CuS to Zn–Sn-codoped CuS NCs as intermediates at 150 °C and finally to quaternary CZTS NCs in the kesterite phase at 220 °C, during which the NCs gradually grow due to the progressive incorporation of foreign cations (Zn2+ and Sn2+) into the as-formed CuS NCs. The introduction of dodecanethiol (DT) leads to the formation of bullet-like CZTS NCs in the wurtzite phase. The Cu-poor CZTS synthesis is reproducible by upscaling the amounts of chemicals and solvents/ligands, which allows for a promising approach to gram-scale production of Cu-based chalcogenides for potential applications in photovoltaics.

ACS Style

Santosh Kumar Verma; Rameshwari Verma; Yi Xie; Dehua Xiong; Wenhui Chen; Chao Hu; Tsiwah Acheampong Emmanuel; Mingqing Wang; Xiujian Zhao. Heat-up and gram-scale synthesis of Cu-poor CZTS nanocrystals with controllable compositions and shapes. CrystEngComm 2017, 19, 2013 -2020.

AMA Style

Santosh Kumar Verma, Rameshwari Verma, Yi Xie, Dehua Xiong, Wenhui Chen, Chao Hu, Tsiwah Acheampong Emmanuel, Mingqing Wang, Xiujian Zhao. Heat-up and gram-scale synthesis of Cu-poor CZTS nanocrystals with controllable compositions and shapes. CrystEngComm. 2017; 19 (15):2013-2020.

Chicago/Turabian Style

Santosh Kumar Verma; Rameshwari Verma; Yi Xie; Dehua Xiong; Wenhui Chen; Chao Hu; Tsiwah Acheampong Emmanuel; Mingqing Wang; Xiujian Zhao. 2017. "Heat-up and gram-scale synthesis of Cu-poor CZTS nanocrystals with controllable compositions and shapes." CrystEngComm 19, no. 15: 2013-2020.

Research article
Published: 23 June 2016 in ACS Applied Materials & Interfaces
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With record cell efficiency of 21.7%, CIGS solar cells have demonstrated to be a very promising photovoltaic (PV) technology. However, their market penetration has been limited due to the inherent high cost of the cells. In this work, in order to lower the cost of CIGS solar cells, all non-vacuum processed CIGS solar cells were designed and developed. CIGS absorber was prepared by annealing of electrodeposited metallic layers in chalcogen atmosphere. Non-vacuum deposited Ag nanowires(NWs)/AZO transparent electrodes(TEs) with good transmittance (92.0% at 550nm) and high conductivity(sheet resistance of 20 Ω/□) were used to replace the vacuum sputtered window layer. Additional thermal treatment after device preparation was conducted at 220̊C for a few of minutes to improve both the value and the uniformity of the efficiency of CIGS pixel cell on 5cm x 5cm substrate. The best performance of the all non-vacuum fabricated CIGS solar cells showed efficiency of 13.74% with Jsc of 34.14mA/cm2, Voc of 0.58V and FF of 69.39% respectively, which is comparable with the efficiency of 14.45% of a reference cell using sputtered window layer.

ACS Style

Mingqing Wang; Kwang-Leong Choy. All-Nonvacuum-Processed CIGS Solar Cells Using Scalable Ag NWs/AZO-Based Transparent Electrodes. ACS Applied Materials & Interfaces 2016, 8, 16640 -16648.

AMA Style

Mingqing Wang, Kwang-Leong Choy. All-Nonvacuum-Processed CIGS Solar Cells Using Scalable Ag NWs/AZO-Based Transparent Electrodes. ACS Applied Materials & Interfaces. 2016; 8 (26):16640-16648.

Chicago/Turabian Style

Mingqing Wang; Kwang-Leong Choy. 2016. "All-Nonvacuum-Processed CIGS Solar Cells Using Scalable Ag NWs/AZO-Based Transparent Electrodes." ACS Applied Materials & Interfaces 8, no. 26: 16640-16648.

Journal article
Published: 26 February 2016 in Scientific Reports
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Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1−xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber|buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells.

ACS Style

Giovanni Altamura; Mingqing Wang; Kwang-Leong Choy. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells. Scientific Reports 2016, 6, 22109 .

AMA Style

Giovanni Altamura, Mingqing Wang, Kwang-Leong Choy. Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells. Scientific Reports. 2016; 6 (1):22109.

Chicago/Turabian Style

Giovanni Altamura; Mingqing Wang; Kwang-Leong Choy. 2016. "Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells." Scientific Reports 6, no. 1: 22109.

Journal article
Published: 01 December 2015 in Thin Solid Films
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Electrostatic spray-assisted vapor deposition (ESAVD) is a non-vacuum, low cost and eco-friendly method to produce Cu(In,Ga)Se2 and Cu2ZnSn(S,Se)4 (CZTSSe) absorbers for thin film solar cells, and it is a very promising method for industrialization due to it is high deposition speed and close to unity deposition efficiency. In this work, in order to improve the efficiency of ESAVD deposited CZTSSe solar cells, an ultrathin ZnO (circa 10 nm) layer was employed as an intermediate layer between CZTSSe and Mo back contact to avoid the direct contact between Mo and CZTSSe and reduce the decomposition of CZTSSe during annealing process. XRF and EDX were used to characterize the chemical composition of CZTSSe before and after selenization respectively. SEM and Raman results showed the improved absorber morphology and the reduced direct interfacial reaction between CZTSSe and Mo. The improvement of the CZTSSe/Mo interface due to the intermediate layer was also reflected in the quality of the derived photovoltaic devices, leading to an improved efficiency of ESAVD-deposited kesterite solar cells from 3.25% to 4.03%.

ACS Style

Giovanni Altamura; Mingqing Wang; Kwang-Leong Choy. Improving efficiency of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells by modification of Mo/absorber interface. Thin Solid Films 2015, 597, 19 -24.

AMA Style

Giovanni Altamura, Mingqing Wang, Kwang-Leong Choy. Improving efficiency of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells by modification of Mo/absorber interface. Thin Solid Films. 2015; 597 ():19-24.

Chicago/Turabian Style

Giovanni Altamura; Mingqing Wang; Kwang-Leong Choy. 2015. "Improving efficiency of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells by modification of Mo/absorber interface." Thin Solid Films 597, no. : 19-24.

Research article
Published: 01 October 2015 in ACS Applied Materials & Interfaces
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Chalcopyrite Cu(In,Ga)(S,Se)2 (CIGSSe) thin films have been deposited by a novel, nonvacuum, and cost-effective electrostatic spray-assisted vapor deposition (ESAVD) method. The generation of a fine aerosol of precursor solution, and their controlled deposition onto a molybdenum substrate, results in adherent, dense, and uniform Cu(In,Ga)S2 (CIGS) films. This is an essential tool to keep the interfacial area of thin film solar cells to a minimum value for efficient charge separation as it helps to achieve the desired surface smoothness uniformity for subsequent cadmium sulfide and window layer deposition. This nonvacuum aerosol based approach for making the CIGSSe film uses environmentally benign precursor solution, and it is cheaper for producing solar cells than that of the vacuum-based thin film solar technology. An optimized CIGSSe thin film solar cell with a device configuration of molybdenum-coated soda-lime glass substrate/CIGSSe/CdS/i-ZnO/AZO shows the photovoltaic (j-V) characteristics of Voc=0.518 V, jsc=28.79 mA cm(-2), fill factor=64.02%, and a promising power conversion efficiency of η=9.55% under simulated AM 1.5 100 mW cm(-2) illuminations, without the use of an antireflection layer. This demonstrates the potential of ESAVD deposition as a promising alternative approach for making thin film CIGSSe solar cells at a lower cost.

ACS Style

Anower Hossain; Mingqing Wang; Kwang-Leong Choy. Ecofriendly and Nonvacuum Electrostatic Spray-Assisted Vapor Deposition of Cu(In,Ga)(S,Se)2 Thin Film Solar Cells. ACS Applied Materials & Interfaces 2015, 7, 22497 -22503.

AMA Style

Anower Hossain, Mingqing Wang, Kwang-Leong Choy. Ecofriendly and Nonvacuum Electrostatic Spray-Assisted Vapor Deposition of Cu(In,Ga)(S,Se)2 Thin Film Solar Cells. ACS Applied Materials & Interfaces. 2015; 7 (40):22497-22503.

Chicago/Turabian Style

Anower Hossain; Mingqing Wang; Kwang-Leong Choy. 2015. "Ecofriendly and Nonvacuum Electrostatic Spray-Assisted Vapor Deposition of Cu(In,Ga)(S,Se)2 Thin Film Solar Cells." ACS Applied Materials & Interfaces 7, no. 40: 22497-22503.

Journal article
Published: 21 August 2014 in Journal of Applied Physics
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We demonstrate an enhancement of photocurrent in hybrid photovoltaic cells based on nanoparticles of zinc oxide (ZnO) and poly(3-hexylthiophene) (P3HT), through molecular interface modification with and without cis-bis(4,4′-dicarboxy-2,2′bipyridine) ruthenium (II) (N3-dye) and α-Sexithiophen-2-yl-phosphonic Acid (6TP) as interface modifiers. We identify the formation of long-lived polarons at P3HT:ZnO interface by means of quasi-steady-state photoinduced absorption (PIA) spectroscopy. Furthermore, by probing the pump-modulation-frequency-dependent PIA signal, we find that P3HT:ZnO-N3 and P3HT:ZnO-6TP exhibit more sharply decaying density with increasing modulation frequency, which is indicative of a longer average lifetime, approximating 1 ms as opposed to ∼0.2 ms without ZnOsurface modification. This highlights the importance of the molecular interface modification in the steady-state polaron dynamics in hybrid solar cells.

ACS Style

Elham Rezasoltani; Mingqing Wang; Ian Hill; Carlos Silva. The influence of molecular interface modification on the charge dynamics of polymeric semiconductor:ZnO heterostructure. Journal of Applied Physics 2014, 116, 074502 .

AMA Style

Elham Rezasoltani, Mingqing Wang, Ian Hill, Carlos Silva. The influence of molecular interface modification on the charge dynamics of polymeric semiconductor:ZnO heterostructure. Journal of Applied Physics. 2014; 116 (7):074502.

Chicago/Turabian Style

Elham Rezasoltani; Mingqing Wang; Ian Hill; Carlos Silva. 2014. "The influence of molecular interface modification on the charge dynamics of polymeric semiconductor:ZnO heterostructure." Journal of Applied Physics 116, no. 7: 074502.