Real-time observation of the buildup of polaron in α-FAPbI 3

• Published in: Nature communications Vol. 14; no. 1; p. 917
• Main Authors: Yue, Xingyu, Wang, Chunwei, Zhang, Bo, Zhang, Zeyu, Xiong, Zhuang, Zu, Xinzhi, Liu, Zhengzheng, Hu, Zhiping, Odunmbaku, George Omololu, Zheng, Yujie, Sun, Kuan, Du, Juan
• Format: Journal Article
• Language: English
• Published: England 17.02.2023

The formation of polaron, i.e., the strong coupling process between the carrier and lattice, is considered to play a crucial role in benefiting the photoelectric performance of hybrid organic-inorganic halide perovskites. However, direct observation of the dynamical formation of polarons occurring at time scales within hundreds of femtoseconds remains a technical challenge. Here, by terahertz emission spectroscopy, we demonstrate the real-time observation of polaron formation process in FAPbI films. Two different polaron resonances interpreted with the anharmonic coupling emission model have been studied: P1 at ~1 THz relates to the inorganic sublattice vibration mode and the P2 at ~0.4 THz peak relates to the FA cation rotation mode. Moreover, P2 could be further strengthened than P1 by pumping the hot carriers to the higher sub-conduction band. Our observations could open a door for THz emission spectroscopy to be a powerful tool in studying polaron formation dynamics in perovskites.