Real-time observation of the buildup of polaron in α-FAPbI3
Xingyu Yue, Chunwei Wang, Bo Zhang, Zeyu Zhang, Zhuang Xiong, Xinzhi Zu, Zhengzheng Liu, Zhiping Hu, George Omololu Odunmbaku, Yujie Zheng, Kuan Sun, Juan Du
Abstract
Abstract 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 3 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.