标题：Passivating Detrimental DX Centers in CH3NH3PbI3 for Reducing Nonradiative Recombination and Elongating Carrier Lifetime
作者：Wang, Jing; Li, Wei; Yin, Wan-Jian*
单位：1 College of Energy Soochow Institute for Energy and Materials InnovationS (SIEMIS) Soochow University Suzhou 215006, China
2 Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies Soochow University Suzhou 215006, China
3 Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China Soochow University Suzhou 215006, China
4 School of Chemistry and Materials Science Hunan Agricultural University Changsha 410128, China
摘要：After a period of rapid, unprecedented development, the growth in the efficiency of perovskite solar cells has recently slowed. Further improvement of cell efficiency will rely on the in-depth understanding and delicate control of defect passivation. Here, the formation mechanism of iodine vacancies (V-I), a typical deep defect in CH3NH3PbI3 (MAPbI(3)), is elucidated. The structural and electronic behaviors of V-I are like those of a DX center, a kind of detrimental defect formed by large atomic displacement. Aided by the passivation mechanism of DX centers in tetrahedral semiconductors, it is found that the introduction of Br strengthens chemical bonds and prevents large atomic displacements during defect charging. It therefore reduces the defect states and diminishes electron-phonon coupling. Using time-domain density functional theory (DFT) combined with nonadiabatic molecular dynamics, it is found that the carrier lifetime can be enhanced from 3.2 ns in defective MAPbI(3) to 19 ns in CH3NH3Pb(I0.96Br0.04)3. This work advances our understanding of how a small amount of Br doping improves the carrier dynamics and cell performance of MAPbI3. It may also provide a route to enhance the carrier lifetimes and efficiencies of perovskite solar cells by defect passivation.