Mixed monomolecular and bimolecular-like recombination processes in CsPbBr${}_3$ perovskite film revealed by time-resolved photoluminescence spectroscopy

Very recently, the newly emerging all inorganic perovskite have attracted a tremendous world-wide attention due to their unique optical properties. Particularly, CsPbBr${}_3$ is a very promising material for many optoelectronic devices. Hence, the understanding of the physics underlying these excellent photo-physical properties is highly required. Herein, we investigated the recombination mechanism in CsPbBr${}_3$ thin film using mainly the power-dependent time-resolved photoluminescence (PLRT) measurements. The photoluminescence (PL) emission in CsPbBr${}_3$ perovskite was suggested to arise from the recombination of free carriers and localized trap states. We have found that the PL is decaying faster at a high excitation power density, from 11.2 to 2.1 ns for the excitation densities between 3.58 and 11.94 W/cm${}^2$. We used a dynamic recombination model to fit the unusual power-dependence transient PL results, from which numerous trap and recombination parameters can be extracted such as the trap density, which was evaluated, ranging from 3.10${}^{15}$ to 10.10${}^{15}$ cm${}^{-3}$ for the excitation densities between 3.58 and 11.94 W/cm${}^2$. Our analysis provides a clear identification of competing monomolecular-like and bimolecular-like recombination processes, These findings shed some light on the interesting luminescence mechanism of CsPbBr${}_3$ perovskite.