关于二维钙钛矿光伏材料的载流子非辐射复合研究发表

张凡关于二维钙钛矿光伏材料的载流子非辐射复合的研究，发表于Physical Review Applied（2022）。

Phonon-assisted nonradiative recombination tuned by organic cations in Ruddlesden-Popper hybrid perovskites

Fan Zhang, Xiaolong Wang, Weiwei Gao*, Jijun Zhao

摘要：

Significant efforts have been devoted to further increasing the photo-conversion efficiency of two-dimensional (2D) organic-inorganic halide perovskites, which are promising photovoltaic materials with superior stability but lower efficiency compared to their three-dimensional counterparts. One of the main factors that limit their photo-conversion efficiency is the nonradiative recombination of photo-excited carriers. A widely used strategy for tuning the photo-conversion efficiency of 2D perovskites is switching various organic cations. However, due to mixed effects contributed from extrinsic factors such as defect concentration and sample morphology, experiments alone are insufficient to explain the role of organic cations in phonon-assisted carrier recombination. With time-domain simulations based on first-principles nonadiabatic molecular dynamics, we investigate six prototypical 2D Ruddlesden-Popper perovskites to reveal the impacts of organic cations on tuning nonradiative recombination time through displacing inorganic ions and affecting electron-phonon coupling. The phonon-assisted band-to-band nonradiative recombination time is on the order of a few hundred nanoseconds and can be tuned up to five times by modifying organic cations. A distinct correlation between pure-dephasing time and inorganic-atom distortions induced by the motion of organic parts has been revealed. Compared to pure-dephasing time, nonadiabatic coupling (NAC) associated with the strength of electron-phonon coupling plays a more important role in determining the nonradiative carrier recombination time. Notably, fluorinated organic spacers increase the NAC between frontier electronic states and speed up the nonradiative recombination process.