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中国物理学会期刊

Ge/Sn合金化对CsPbBr3钙钛矿热载流子弛豫影响的非绝热分子动力学研究

CSTR: 32037.14.aps.73.20231061

Nonadiabatic molecular dynamics study on effect of Ge/Sn alloy on hot carrier relaxation of CsPbBr3 perovskite

CSTR: 32037.14.aps.73.20231061
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  • 铯基全无机钙钛矿CsPbBr3具有良好的热稳定性, 在应用中表现出优越的发光特性, 是近年来光电领域的明星材料. CsPbBr3界面的光生载流子过程与其光电性能密切相关. 本文采用非绝热分子动力学方法结合含时密度泛函理论, 对CsPbBr3及其合金化结构的激发态动力学过程进行了系统研究. 研究结果表明, Sn/Ge合金化能够有效缩短退相干时间, 减缓电子-空穴复合. CsPb0.75Ge0.25Br3体系的载流子寿命延长至1.6倍, 而CsPb0.5Ge0.25Sn0.25Br3体系的载流子寿命延长为原始体系的4.2倍. 证明了B位(钙钛矿结构ABX3中的B位)金属阳离子的双原子合金化对CsPbBr3的非辐射电子-空穴复合具有很强的影响. 本研究提供了一种能够有效延长钙钛矿载流子寿命, 合理优化太阳能电池性能的合金化方案, 为未来钙钛矿太阳能电池材料的设计提供了思路.

     

    Perovskite solar cells have been a prominent focus in the field of photovoltaics in recent decades, owing to their exceptional performance: easy synthesis, and cost-effectiveness. The all-inorganic cesium-based perovskite CsPbBr3, known for its remarkable thermal stability, has become a star material in the field of optoelectronics due to its outstanding luminescent properties. Despite the high efficiency of lead-based perovskite solar cells, the toxicity associated with lead and the poor long-term stability of these devices remain significant barriers to their large-scale commercialization. As is well known, non-radiative electron-hole recombination significantly shortens the carrier lifetime, acting as a primary pathway for excited state charge to loss energy. This phenomenon directly affects the photovoltaic conversion efficiency and charge transfer performance of perovskite materials. Therefore, maximizing the reduction of non-radiative recombination energy loss in perovskite solar cells has become a crucial research focus. In this study, a systematic exploration is conducted by using a non-adiabatic molecular dynamics approach combined with time-dependent density functional theory to investigate the excited-state carrier dynamics of CsPbBr3 and its alloyed structures, CsPb0.75Ge0.25Br3 and CsPb0.5Ge0.25Sn0.25Br3. The study comprehensively analyzes the non-radiative electron-hole recombination scenarios and the mechanisms for reducing charge energy loss based on crystal structure, electronic properties, and excited-state properties. The research findings reveal that alloying with Sn/Ge can reduce the bandgap, increase non-adiabatic coupling, and shorten the decoherence time. The interplay of reduced quantum decoherence, smaller bandgap, and larger non-adiabatic coupling effectively decelerates the electron-hole recombination process. Consequently, the carrier lifetime of the CsPb0.75Ge0.25Br3 system extends by 1.6 times. Moreover, under the joint influence of Sn/Ge, the carrier lifetime of the CsPb0.5Ge0.25Sn0.25Br3 system extends by 4.2 times compared with those of the original system. The overall sequence follows CsPb0.5Ge0.25Sn0.25Br3 > CsPb0.75Ge0.25Br3 > CsPbBr3. This study underscores the significant influence of binary alloying of B-site metal cations (in the perovskite structure ABX3, where B-site refers to the metal cation) on the non-radiative electron-hole recombination of CsPbBr3.This research presents an effective alloying scheme that substantially prolongs the carrier lifetime of perovskites, offering a rational approach to optimizing solar cell performance. It lays the groundwork for the future design of perovskite solar cell materials.

     

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