Suppressing Ion Migration across Perovskite Grain Boundaries by Polymer Additives |
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Authors: | Yuhui Ma Yuanhang Cheng Xiuwen Xu Menglin Li Chujun Zhang Sin Hang Cheung Zixin Zeng Dong Shen Yue-Min Xie Ka Lok Chiu Fen Lin Shu Kong So Chun-Sing Lee Sai-Wing Tsang |
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Affiliation: | 1. Department of Materials Science and Engineering, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Hong Kong SAR, 999077 P. R. China;2. Solar Energy Research Institute of Singapore (SERIS), National University of Singapore (NUS), Singapore, 117574 Singapore;3. Department of Physics, Hong Kong Baptist University, Hong Kong SAR, 999077 P. R. China;4. Department of Chemistry, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Hong Kong SAR, 999077 P. R. China |
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Abstract: | Passivation of organometal halide perovskites with polar molecules has been recently demonstrated to improve the photovoltaic device efficiency and stability. However, the mechanism is still elusive. Here, it is found that both polymers with large and small dipole moment of 3.7 D and 0.6 D have negligible defect passivation effect on the MAPbI3 perovskite films as evidenced by photothermal deflection spectroscopy. The photovoltaic devices with and without the polymer additives also have comparable power conversion efficiencies around 19%. However, devices with the additives have noticeable improvement in stability under continuous light irradiation. It is found that although the initial mobile ion concentrations are comparable in both devices with and without the additives, the additives can strongly suppress the ion migration during the device operation. This contributes to the significantly enhanced electrical-field stress tolerance of the perovskite solar cells (PVSCs). The PVSCs with polymer additives can operate up to −2 V reverse voltage bias which is much larger than the breakdown voltage of −0.5 V that has been commonly observed. This study provides insight into the role of additives in perovskites and the corresponding device degradation mechanism. |
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Keywords: | grain boundaries ion dissociation ion migration perovskite polymer additives |
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