The Experts below are selected from a list of 28620 Experts worldwide ranked by ideXlab platform
Shanshan Zhang - One of the best experts on this subject based on the ideXlab platform.
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defect interface Recombination limited quasi fermi level splitting and open circuit voltage in mono and triple cation perovskite solar cells
ACS Applied Materials & Interfaces, 2020Co-Authors: Paul Meredith, Shanshan Zhang, Paul E Shaw, Guanran Zhang, Hui Jin, Meiqian Tai, Hong Lin, Paul L Burn, Dieter NeherAbstract:Multication metal-halide perovskites exhibit desirable performance and stability, compared to their monocation counterparts. However, the study of the photophysical properties and the nature of defect states in these materials is still a challenging and ongoing task. Here, we study bulk and interfacial energy Loss mechanisms in solution-processed MAPbI3 (MAPI) and (CsPbI3)0.05[(FAPbI3)0.83(MAPbBr3)0.17]0.95 (triple cation) perovskite solar cells using absolute photoluminescence (PL) measurements. In neat MAPI films, we find a significantly smaller quasi-Fermi level splitting than for the triple cation perovskite absorbers, which defines the open-circuit voltage of the MAPI cells. PL measurements at low temperatures (∼20 K) on MAPI films demonstrate that emissive subgap states can be effectively reduced using different passivating agents, which lowers the nonradiative Recombination Loss at room temperature. We conclude that while triple cation perovskite cells are limited by interfacial Recombination, the passivation of surface trap states within the MAPI films is the primary consideration for device optimization.
Alex K Y Jen - One of the best experts on this subject based on the ideXlab platform.
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quantifying efficiency Loss of perovskite solar cells by a modified detailed balance model
Advanced Energy Materials, 2018Co-Authors: Wei E I Sha, Alex K Y Jen, Hong Zhang, Zi Shuai Wang, Hugh L Zhu, Xingang Ren, Francis Lin, Wallace C H ChoyAbstract:A modified detailed balance model is built to understand and quantify efficiency Loss of perovskite solar cells. The modified model captures the light-absorption-dependent short-circuit current, contact and transport-layer-modified carrier transport, as well as Recombination and photon-recycling-influenced open-circuit voltage. The theoretical and experimental results show that for experimentally optimized perovskite solar cells with the power conversion efficiency of 19%, optical Loss of 25%, nonradiative Recombination Loss of 35%, and ohmic Loss of 35% are the three dominant Loss factors for approaching the 31% efficiency limit of perovskite solar cells. It is also found that the optical Loss climbs up to 40% for a thin-active-layer design. Moreover, a misconfigured transport layer introduces above 15% of energy Loss. Finally, the perovskite-interface-induced surface Recombination, ohmic Loss, and current leakage should be further reduced to upgrade device efficiency and eliminate hysteresis effect. This work contributes to fundamental understanding of device physics of perovskite solar cells. The developed model offers a systematic design and analysis tool to photovoltaic science and technology.
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quantifying efficiency Loss of perovskite solar cells by a modified detailed balance model
arXiv: Applied Physics, 2018Co-Authors: Wei E I Sha, Alex K Y Jen, Hong Zhang, Zi Shuai Wang, Hugh L Zhu, Xingang Ren, Francis Lin, Wallace C H ChoyAbstract:A modified detailed balance model is built to understand and quantify efficiency Loss of perovskite solar cells. The modified model captures the light-absorption dependent short-circuit current, contact and transport-layer modified carrier transport, as well as Recombination and photon-recycling influenced open-circuit voltage. Our theoretical and experimental results show that for experimentally optimized perovskite solar cells with the power conversion efficiency of 19%, optical Loss of 25%, non-radiative Recombination Loss of 35%, and ohmic Loss of 35% are the three dominant Loss factors for approaching the 31% efficiency limit of perovskite solar cells. We also find that the optical Loss will climb up to 40% for a thin-active-layer design. Moreover, a misconfigured transport layer will introduce above 15% of energy Loss. Finally, the perovskite-interface induced surface Recombination, ohmic Loss, and current leakage should be further reduced to upgrade device efficiency and eliminate hysteresis effect. The work contributes to fundamental understanding of device physics of perovskite solar cells. The developed model offers a systematic design and analysis tool to photovoltaic science and technology.
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a copper doped nickel oxide bilayer for enhancing efficiency and stability of hysteresis free inverted mesoporous perovskite solar cells
Nano Energy, 2017Co-Authors: Kai Yao, Xiaofeng Wang, Yihua Jiang, Haitao Huang, Alex K Y JenAbstract:Abstract Although the inverted perovskite solar cells (PeSCs) have many advantages such as simple device fabrication, high stability and small hysteresis, the efficiency of inverted mesoporous PeSCs are still lower than those of normal-structure. For developing inverted mesoporous perovskite solar cells and the future design of tandem devices, a p-type metal oxide with high surface area and good charge carrier mobility is of paramount importance. Here, we develop a bilayer structure of p-type Cu:NiOx nanoparticle-based mesoporous and Cu-doped NiOx blocking layers to achieve efficient charge collection at the NiOx/perovskite interface with minimized Recombination Loss. Our strategy enables the fabrication of centimeter-sized perovskite solar cells with a decent efficiency of 18.1%, significantly improved stability, and negligible hysteresis. The rational design of the p-type Cu-doped metal oxide bilayer provides an effective strategy for future development of inverted architecture based mesoporous solar cells.
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polymer triplet energy levels need not limit photocurrent collection in organic solar cells
Journal of the American Chemical Society, 2012Co-Authors: Cody W Schlenker, Alex K Y Jen, Kungshih Chen, Hinlap Yip, Liam R Bradshaw, Stefan T Ochsenbein, Feizhi Ding, Daniel R Gamelin, David S GingerAbstract:We study charge Recombination via triplet excited states in donor/acceptor organic solar cells and find that, contrary to intuition, high internal quantum efficiency (IQE) can be obtained in polymer/fullerene blend devices even when the polymer triplet state is significantly lower in energy than the intermolecular charge transfer (CT) state. Our model donor system comprises the copolymer PIDT-PhanQ: poly(indacenodithiophene-co-phenanthro[9,10-b]quinoxaline), which when blended with phenyl-C71-butyric acid methyl ester (PC71BM) is capable of achieving power conversion efficiencies of 6.0% and IQE ≈ 90%, despite the fact that the polymer triplet state lies 300 meV below the interfacial CT state. However, as we push the open circuit voltage (VOC) higher by tailoring the fullerene reduction potential, we observe signatures of a new Recombination Loss process near VOC = 1.0 V that we do not observe for PCBM-based devices. Using photoinduced absorption and photoluminescence spectroscopy, we show that a new reco...
Dieter Neher - One of the best experts on this subject based on the ideXlab platform.
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defect interface Recombination limited quasi fermi level splitting and open circuit voltage in mono and triple cation perovskite solar cells
ACS Applied Materials & Interfaces, 2020Co-Authors: Paul Meredith, Shanshan Zhang, Paul E Shaw, Guanran Zhang, Hui Jin, Meiqian Tai, Hong Lin, Paul L Burn, Dieter NeherAbstract:Multication metal-halide perovskites exhibit desirable performance and stability, compared to their monocation counterparts. However, the study of the photophysical properties and the nature of defect states in these materials is still a challenging and ongoing task. Here, we study bulk and interfacial energy Loss mechanisms in solution-processed MAPbI3 (MAPI) and (CsPbI3)0.05[(FAPbI3)0.83(MAPbBr3)0.17]0.95 (triple cation) perovskite solar cells using absolute photoluminescence (PL) measurements. In neat MAPI films, we find a significantly smaller quasi-Fermi level splitting than for the triple cation perovskite absorbers, which defines the open-circuit voltage of the MAPI cells. PL measurements at low temperatures (∼20 K) on MAPI films demonstrate that emissive subgap states can be effectively reduced using different passivating agents, which lowers the nonradiative Recombination Loss at room temperature. We conclude that while triple cation perovskite cells are limited by interfacial Recombination, the passivation of surface trap states within the MAPI films is the primary consideration for device optimization.
Jianxin Tang - One of the best experts on this subject based on the ideXlab platform.
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surface induced phase engineering and defect passivation of perovskite nanograins for efficient red light emitting diodes
Nanoscale, 2021Co-Authors: Yu Tian, Yang Shen, Jianxin Tang, Xiaoyi Cai, Kongchao Shen, Xingyu Gao, Fei Song, Wenjun WangAbstract:Organic-inorganic hybrid lead halide perovskites are potential candidates for next-generation light-emitting diodes (LEDs) in terms of tunable emission wavelengths, high electroluminescence efficiency, and excellent color purity. However, the device performance is still limited by severe non-radiative Recombination Losses and operational instability due to a high degree of defect states on the perovskite surface. Here, an effective surface engineering method is developed via the assistance of guanidinium iodide (GAI), which allows the formation of surface-2D heterophased perovskite nanograins and surface defect passivation due to the bonding with undercoordinated halide ions. Efficient and stable red-emission LEDs are realized with the improved optoelectronic properties of GAI-modified perovskite nanograins by suppressing the trap-mediated non-radiative Recombination Loss. The champion device with a high color purity at 692 nm achieves an external quantum efficiency of 17.1%, which is 2.3 times that of the control device. Furthermore, the operational stability is highly improved, showing a half-lifetime of 563 min at an initial luminance of 1000 cd m-2. The proposed GAI-assisted surface engineering is a promising approach for defect passivation and phase engineering in perovskite films to achieve high-performance perovskite LEDs.
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synergetic transparent electrode architecture for efficient non fullerene flexible organic solar cells with 12 efficiency
ACS Nano, 2019Co-Authors: Yuexing Zhang, Jin Fang, Yang Shen, Jingde Chen, Sara Pelivani, Maojie Zhang, Jianxin TangAbstract:Flexible organic solar cells (OSCs) are considered one key component in wearable, intelligent electronics due to the unique capacity for highly flexible renewable energy sources. However, it is urgently required to enhance their efficiency, as it is far inferior to that of their conventional, glass-based counterparts. To boost the performance of flexible OSCs on plastic substrates, we here present a synergetic transparent electrode structure, which combines electrically conductive silver nanowires, a sol–gel-derived ZnO planarization layer, and imprinted light-trapping nanostructures. This synergetic composite electrode exhibits good properties in terms of optical transparency, electrical conductivity, mechanical flexibility, and low-temperature processability. As a result, the single-junction non-fullerene-based flexible OSCs achieve a power conversion efficiency exceeding 12% due to the synergetic interplay between broadband light trapping and suppressed charge Recombination Loss. Moreover, these flexib...
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polymer solar cells with 90 external quantum efficiency featuring an ideal light and charge manipulation layer
Advanced Materials, 2018Co-Authors: Jingde Chen, Yuexing Zhang, Jingshuai Zhu, Qianqian Zhang, Jingsheng Huang, Xiaowei Zhan, Wei You, Jianxin TangAbstract:Rapid progress in the power conversion efficiency (PCE) of polymer solar cells (PSEs) is beneficial from the factors that match the irradiated solar spectrum, maximize incident light absorption, and reduce photogenerated charge Recombination. To optimize the device efficiency, a nanopatterned ZnO:Al2 O3 composite film is presented as an efficient light- and charge-manipulation layer (LCML). The Al2 O3 shells on the ZnO nanoparticles offer the passivation effect that allows optimal electron collection by suppressing charge-Recombination Loss. Both the increased refractive index and the patterned deterministic aperiodic nanostructure in the ZnO:Al2 O3 LCML cause broadband light harvesting. Highly efficient single-junction PSCs for different binary blends are obtained with a peak external quantum efficiency of up to 90%, showing certified PCEs of 9.69% and 13.03% for a fullerene blend of PTB7:PC71 BM and a nonfullerene blend, FTAZ:IDIC, respectively. Because of the substantial increase in efficiency, this method unlocks the full potential of the ZnO:Al2 O3 LCML toward future photovoltaic applications.
Yang Yang - One of the best experts on this subject based on the ideXlab platform.
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amphoteric imidazole doping induced large grained perovskite with reduced defect density for high performance inverted solar cells
Solar Energy Materials and Solar Cells, 2020Co-Authors: Yu Wang, Yang Yang, Dongwei Han, Qifeng Yang, Quan Yuan, Ying Yang, Dongying Zhou, Lai FengAbstract:Abstract Intrinsic defect density in polycrystalline halide perovskite films are required to be low enough to suppress charge Recombination Loss for improvement in performance of perovskite solar cells (PeSCs). In this paper, we propose the use of amphoteric imidazole to achieve high crystalline quality of CH3NH3PbI3 perovskite absorption layer. The imidazole additive plays a synergistic role in controlling the perovskite crystal growth for large grain size and passivating the uncoordinated ions (e.g., Pb2+) defects, resulting in improved carrier transport/lifetime and suppressed non-radiative Recombination. The champion power conversion efficiency (PCE) of PeSCs with imidazole is improved to 16.88%, from the control device with a PCE value of 14.65%. Besides, the stability of imidazole modified perovskite films is further improved by limiting ion immigration at grain boundaries against moisture and heat stresses. The findings pave an avenue for synergistically modulating crystallization and healing defect in perovskite to achieve efficient and stable solar cells.
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multifunctional fullerene derivative for interface engineering in perovskite solar cells
Journal of the American Chemical Society, 2015Co-Authors: Yiming Zhao, Lei Meng, Qi Chen, Yang Michael Yang, Yongsheng Liu, Ziruo Hong, Zonghao Liu, Yaotsung Hsieh, Yang YangAbstract:In perovskite based planar heterojunction solar cells, the interface between the TiO2 compact layer and the perovskite film is critical for high photovoltaic performance. The deep trap states on the TiO2 surface induce several challenging issues, such as charge Recombination Loss and poor stability etc. To solve the problems, we synthesized a triblock fullerene derivative (PCBB-2CN-2C8) via rational molecular design for interface engineering in the perovskite solar cells. Modifying the TiO2 surface with the compound significantly improves charge extraction from the perovskite layer. Together with its uplifted surface work function, open circuit voltage and fill factor are dramatically increased from 0.99 to 1.06 V, and from 72.2% to 79.1%, respectively, resulting in 20.7% improvement in power conversion efficiency for the best performing devices. Scrutinizing the electrical properties of this modified interfacial layer strongly suggests that PCBB-2CN-2C8 passivates the TiO2 surface and thus reduces charge Recombination Loss caused by the deep trap states of TiO2. The passivation effect is further proven by stability testing of the perovskite solar cells with shelf lifetime under ambient conditions improved by a factor of more than 4, from ∼40 h to ∼200 h, using PCBB-2CN-2C8 as the TiO2 modification layer. This work offers not only a promising material for cathode interface engineering, but also provides a viable approach to address the challenges of deep trap states on TiO2 surface in planar perovskite solar cells.
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hole selective nio contact for efficient perovskite solar cells with carbon electrode
Nano Letters, 2015Co-Authors: Zonghao Liu, Yang Yang, Qi Chen, Zhixiang Zuo, Meng Zhang, Zhixin Zhao, Yan Shen, Huanping Zhou, Mingkui WangAbstract:In this study, we communicate an investigation on efficient CH3NH3PbI3-based solar cells with carbon electrode using mesoporous TiO2 and NiO layers as electron and hole selective contacts. The device possesses an appreciated power conversion efficiency of 14.9% under AM 1.5G illumination. The detailed information can be disclosed with impedance spectroscopy via tuning the interfaces between CH3NH3PbI3 and different charge selective contacts. The results clearly show charge accumulation at the interface of CH3NH3PbI3. The NiO is believed to efficiently accelerate charge extraction to the external circuit. The extracted charge could improve photovoltaic performance by shifting hole Fermi level down, achieving a high device photovoltage. A fast interfacial Recombination at the interface of CH3NH3PbI3/electron selective contact layer (mesoporous TiO2), occurring in millisecond domains, is the critical issue for charge carrier Recombination Loss.