Electron-Phonon Coupling in Two-Dimensional Ruddlesden–Popper Hybrid Perovskites

Abstract

Two-dimensional lead halide perovskites are considered low-cost and relatively stable materials for high-efficiency photovoltaic applications. Photoexcitation of lead halide perovskite materials leads to the generation of charge carriers. Understanding the charge carrier dynamics, especially at the early stage of their generation, is crucial for improving photovoltaic efficiency. Amongst various dynamical features, investigation of the interaction between the carriers and lattice modes provides crucial information about the behavior of the photoexcited carriers. Effective interaction between charge carriers and lattice modes often produces polarons, which are considered to influence the charge carrier transport properties and thereby the photovoltaic efficiencies. In this feature article, we discuss the recent development on various methods, including temperature-dependent photoluminescence (PL) and femtosecond transient absorption (fs-TA) spectroscopies for the detection of electron-phonon coupling. While the temperature-dependent PL measurement provides an easy way of detection of electron-phonon coupling phenomenon, fs-TA could deliver more compressive understanding of the processes. We further discuss on how the electron-phonon coupling affects various important properties in 2D halide perovskite films such as band gap modulation, PL behavior, self-trapped exciton formation and hot carrier cooling rates which are crucial to study for perovskite optoelectronics.