Cong Muyu, Yang Bin, Chen Junsheng, Hong Feng, Yang Songqiu, Deng Weiqiao, Han Keli
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, P. R. China.
University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
J Phys Chem Lett. 2020 Mar 5;11(5):1921-1926. doi: 10.1021/acs.jpclett.0c00188. Epub 2020 Feb 24.
Carrier multiplication (CM) is an effective mechanism that makes it possible to use hot carriers (HCs) to bypass the Shockley-Queisser limit for solar-cell efficiency. In this paper, we present a detailed study of both CM and HC cooling dynamics in quantum-confined CsPbI perovskite nanocrystals (NCs), using femtosecond transient absorption spectroscopy. Our results show that barrierless CM, with an efficiency exceeding 90%, can be achieved in strongly confined NCs on a time scale of ≪200 fs. A low CM efficiency (∼40%), however, is observed in weakly confined NCs. HC cooling dynamics suggests the absence of an intrinsic phonon bottleneck in strongly confined NCs. Furthermore, the biexciton Auger rate increased 4-fold in strongly confined NCs compared to that in weakly confined NCs. These results suggest that the enhanced CM in strongly confined NCs likely originates from enhanced Coulomb coupling and relaxed momentum conservation.
载流子倍增（CM）是一种有效的机制，它使得利用热载流子（HCs）绕过太阳能电池效率的肖克利-奎塞尔极限成为可能。在本文中，我们使用飞秒瞬态吸收光谱对量子限域的CsPbI钙钛矿纳米晶体（NCs）中的CM和HC冷却动力学进行了详细研究。我们的结果表明，在强限域的NCs中，在≪200 fs的时间尺度上可以实现效率超过90%的无障碍CM。然而，在弱限域的NCs中观察到较低的CM效率（约40%）。HC冷却动力学表明在强限域的NCs中不存在固有的声子瓶颈。此外，与弱限域的NCs相比，强限域的NCs中的双激子俄歇速率增加了4倍。这些结果表明，强限域的NCs中增强的CM可能源于增强的库仑耦合和放宽的动量守恒。
