Congratulations to Pro. Sun Kuan of the research group and Zhang Zeyu & Du Juan's team from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, for publishing the results in Nature Communications. This work demonstrates the real-time observation of polaron formation in FAPbI3 thin films through terahertz emission spectroscopy.

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 FAPbI3 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.

Original Link: https://www.nature.com/articles/s41467-023-36652-4