东南大学王金兰团队提出了点缺陷对卤化铅钙钛矿热载流子冷却的控制。相关研究成果发表在2022年9月20日出版的《美国化学会杂志》。

卤化铅钙钛矿中的热载流子（HCs）很容易在频带边缘迅速松弛，浪费大量光子能量，严重限制了其作为HC光伏器件的转换效率。

该文中，研究人员阐明了具有常见空位点缺陷（如MAv+和Iv-）和间隙点缺陷（例如Ii-）的MAPbI₃钙钛矿的HC冷却动力学，并使用从头算非绝热分子动力学解释了潜在物理机制。与空位点缺陷相反，间隙点缺陷降低了能带简并度，降低了HC声子相互作用，减弱了非绝热耦合，并最终将热电子冷却速度减慢了1.5–2倍。热电子冷却和热空穴冷却分别揭示了逐带弛豫路径和直接弛豫通道，解释为什么热电子在冷却过程中比热空穴储存更多的能量。

此外，与Ii相互作用的氧分子急剧加速了热电子冷却，使其速度比原始系统更快，并揭示了氧对HC冷却的有害影响。

该项工作为缺陷相关HC冷却动力学提供了重要的见解，并提出了一种设计高效HC光伏器件的新策略。

附：英文原文

Title: Control of Hot Carrier Cooling in Lead Halide Perovskites by Point Defects

Author: Zhaobo Zhou, Junjie He, Thomas Frauenheim, Oleg V. Prezhdo, Jinlan Wang

Issue&Volume: September 20, 2022

Abstract: Hot carriers (HCs) in lead halide perovskites are prone to rapidly relax at the band edge and waste plentiful photon energy, severely limiting their conversion efficiency as HC photovoltaic devices. Here, the HC cooling dynamics of MAPbI3 perovskite with common vacancy point defects (e.g., MAv+ and Iv–) and an interstitial point defect (e.g., Ii–) is elucidated, and the underlying physics is explicated using ab initio nonadiabatic molecular dynamics. Contrary to vacancy point defects, the interstitial point defect reduces the band degeneracy, decreases the HC phonon interaction, weakens the nonadiabatic coupling, and ultimately slows down hot electron cooling by a factor of 1.5–2. Furthermore, the band-by-band relaxation pathway and direct relaxation pathway are uncovered for hot electron cooling and hot hole cooling, respectively, explaining why hot electrons can store more energy than hot holes during the cooling process. Besides, oxygen molecules interacting with Ii– sharply accelerate the hot electron cooling, making it even faster than that of the pristine system and revealing the detrimental effect of oxygen on HC cooling. This work provides significant insights into the defect-dependent HC cooling dynamics and suggests a new strategy to design high-efficiency HC photovoltaic devices.

DOI: 10.1021/jacs.2c08487

Source: https://pubs.acs.org/doi/10.1021/jacs.2c08487