Evidence of polaron formation in halide perovskites via carrier effective mass measurements

• Main Authors: Bao, Di, Chang, Qing, Chen, Bingbing, Chen, Xiaoxuan, Sun, Handong, Lam, Yeng Ming, Zhao, Daming, Zhu, Jian-Xin, Chia, Elbert E.M.
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Materials; Science::Physics; Polaron Formation; Halide Perovskites
• Online Access: https://hdl.handle.net/10356/170872
• Institution: Nanyang Technological University

Carrier effective mass is a central parameter in solid-state physics. It is a measure of the strength of the coupling between a carrier and excitations arising from its surrounding medium, and features prominently in transport and optical calculations. Experimental techniques employed to determine it are steady-state ones, and so are unable to detect any change in the effective mass after a strong perturbation to the system, e.g., strong optical excitation. By combining time-resolved terahertz spectroscopy and transient absorption spectroscopy, on a mixed-cation mixed-halide perovskite thin film, we observe a large and long-lived photoinduced enhancement of the carrier effective mass, and from it deduce a twofold increase of the carrier-phonon coupling constant, giving evidence of polaron formation. Our work demonstrates a new approach to track the strength and ultrafast lifetimes of photoinduced carrier-boson interactions down to picosecond timescales that can be applied to a wide range of solid-state systems.