摘要
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.
Abstract
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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