Exciton and lattice dynamics in low-temperature processable CsPbBr3 thin-films

Abstract

Lead-halide based perovskite semiconductors have recently attracted significant attention owing to their rapidly increasing efficiency in solar cells and light-emitting devices. Organic–inorganic lead halide perovskites have gained popularity due to their low-temperature solution processability, low electronic defect density and low structural and thermal disorder. Nonetheless, their single crystals suffer from lower carrier mobility (∼10–100 cm2 V−1 s−1) than those in inorganic semiconductors and slow radiative recombination rates, with average lifetimes exceeding one μs. Recently, CsPbBr3, an all-inorganic lead-bromide perovskite also attracted great attention due to its high thermal stability and fast radiative recombination. Therefore, it is required to explore the exciton and lattice dynamics of solution processed CsPbBr3 thin films. Here, we show that CsPbBr3 exhibits an electron–phonon coupling strength (∼70 meV) comparable with its organic–inorganic hybrid perovskite counterpart CH3NH3PbBr3 (∼60 meV). The main source of electron–phonon coupling was identified to be the longitudinal-optical phonon mode of the PbBr lattice vibration at ∼20 meV. Carrier recombination studies by temperature-dependent steady-state and time-resolved photoluminescence revealed that recombination occurred from lattice-bound carriers at room-temperature and in inert atmosphere. Carrier lifetimes are short and show a distinct temperature-dependence. All findings are supported by first-principles calculations in the framework of density-functional theory.