Wang Yutong, Fang Wei-Hai, Long Run, Prezhdo Oleg V
College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P. R. China.
Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States.
J Phys Chem Lett. 2019 Apr 4;10(7):1617-1623. doi: 10.1021/acs.jpclett.9b00763. Epub 2019 Mar 25.
The influence of grain boundaries (GBs) on charge carrier lifetimes in methylammonium lead triiodide perovskite (MAPbI) remains unclear. Some experiments suggest that GBs promote rapid nonradiative decay and deteriorate device performance, while other measurements indicate that charge recombination happens primarily in non-GB regions and that GBs facilitate charge separation and collection. By combining time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we demonstrate that charge separation and localization happening at MAPbI GBs due to symmetry breaking suppresses charge recombination. Even though GBs lower the MAPbI bandgap and charge localization enhances interactions with phonons, electron-hole separation decreases the NA coupling, and the excited state lifetime remains virtually unchanged compared to the pristine perovskite. Our study rationalizes how GBs can have a positive influence on perovskite optoelectronic properties and advances fundamental understanding of charge carrier dynamics in these fascinating materials.
晶界（GBs）对甲基铵碘化铅钙钛矿（MAPbI）中电荷载流子寿命的影响尚不清楚。一些实验表明，晶界会促进快速的非辐射衰减并降低器件性能，而其他测量结果则表明，电荷复合主要发生在非晶界区域，并且晶界有助于电荷分离和收集。通过结合时域密度泛函理论和非绝热（NA）分子动力学，我们证明了由于对称性破缺在MAPbI晶界处发生的电荷分离和局域化抑制了电荷复合。尽管晶界降低了MAPbI的带隙，并且电荷局域化增强了与声子的相互作用，但电子-空穴分离降低了非绝热耦合，并且与原始钙钛矿相比，激发态寿命实际上保持不变。我们的研究解释了晶界如何对钙钛矿的光电性能产生积极影响，并推进了对这些迷人材料中电荷载流子动力学的基本理解。
