多晶MAPbBr3薄膜中束缚载流子热发射复合过程

Thermal emission recombination process of trapped carriers in polycrystalline MAPbBr3 films

摘要:

有机-无机卤化铅钙钛矿(organic inorganic lead halide perovskite,OLHP)半导体材料内部的陷阱是影响OLHP的光电性能的重要因素。为了理解多晶的甲胺溴基钙钛矿((Methylammonium)PbBr₃,MAPbBr₃)薄膜中陷阱对光生载流子复合的影响,本文采用了时间分辨微波光电导(time resolved microwave conductivity,TRMC)技术探究了多晶MAPbBr₃薄膜的光生载流子复合动力学过程。实验测量结果表明多晶MAPbBr₃薄膜的载流子复合过程包括自由载流子复合与束缚载流子的热发射复合两部分。其中,与束缚载流子热发射复合相关的能级远离连续带,且对应的能级深度约为0.6 eV,分布宽度约为89.2 meV。本文同时利用变激发波长TRMC对比实验,分析浅束缚光生电子与导带光生电子复合过程的差异。相比于导带上的电子,实验结果表明浅束缚电子跃迁到深束缚能级的概率更大。

Abstract:

The trap inside the organic-inorganic lead halide perovskite (OLHP) semiconductor materials is crucial factor for its photoelectric properties.In order to understand the effect of trap on carrier recombination process in polycrystalline methylamine bromide perovskite ((Methylammonium)PbBr₃,MAPbBr₃) films,time resolved microwave conductivity (TRMC) technology is applied.The experimental results show that both free carrier recombination and trapped carrier thermally emission recombination occur to polycrystalline MAPbBr₃ films.The energy level related to trapped carrier thermal emission recombination isolate from continuous band, and their central energy depth and distribution width are 0.6 eV and 89.2 meV,respectively.Excitation wavelength varying TRMC experiments are also used to differentiate shallow trapped electrons and electrons in conduction band.The experiments confirm that shallow trapped electrons are more likely to transition to deep trapped states compared with electrons on coduction band.