Boehme Simon C, Brinck Stephanie Ten, Maes Jorick, Yazdani Nuri, Zapata Felipe, Chen Kai, Wood Vanessa, Hodgkiss Justin M, Hens Zeger, Geiregat Pieter, Infante Ivan
Department of Theoretical Chemistry, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Department of Chemistry, Faculty of Sciences, Universiteit Gent, Krijgslaan 281, 9000 Gent, Belgium.
Nano Lett. 2020 Mar 11;20(3):1819-1829. doi: 10.1021/acs.nanolett.9b05051. Epub 2020 Feb 18.
We combine state-of-the-art ultrafast photoluminescence and absorption spectroscopy and nonadiabatic molecular dynamics simulations to investigate charge-carrier cooling in CsPbBr nanocrystals over a very broad size regime, from 0.8 to 12 nm. Contrary to the prevailing notion that polaron formation slows down charge-carrier cooling in lead-halide perovskites, no suppression of carrier cooling is observed in CsPbBr nanocrystals except for a slow cooling (over ∼10 ps) of "warm" electrons in the vicinity (within ∼0.1 eV) of the conduction band edge. At higher excess energies, electrons and holes cool with similar rates, on the order of 1 eV ps carrier, increasing weakly with size. Our ab initio simulations suggest that cooling proceeds via fast phonon-mediated intraband transitions driven by strong and size-dependent electron-phonon coupling. The presented experimental and computational methods yield the spectrum of involved phonons and may guide the development of devices utilizing hot charge carriers.
我们结合了最先进的超快光致发光和吸收光谱以及非绝热分子动力学模拟，以研究CsPbBr纳米晶体在0.8至12纳米的非常宽的尺寸范围内的电荷载流子冷却情况。与极化子形成会减缓卤化铅钙钛矿中电荷载流子冷却的普遍观点相反，在CsPbBr纳米晶体中未观察到载流子冷却受到抑制，除了导带边缘附近（约0.1 eV范围内）的“热”电子有缓慢冷却（约10皮秒）。在更高的过剩能量下，电子和空穴以相似的速率冷却，约为1 eV/皮秒，且随尺寸微弱增加。我们的从头算模拟表明，冷却是通过由强且与尺寸相关的电子 - 声子耦合驱动的快速声子介导的带内跃迁进行的。所提出的实验和计算方法得出了所涉及声子的光谱，并可能指导利用热电荷载流子的器件的开发。
