Insight into Photon Recycling in Perovskite Semiconductors from the Concept of Photon Diffusion

Photon recycling has been proven to be an important process in metal halide perovskite thin films. We propose a model of photon recycling based on the photon diffusion concept that can interpret experimental observations on the photoluminescence and transient spectroscopy in perovskite layers. Our model shows how the photon recycling can enhance the apparent photocarrier lifetime and thereby slow down the photoluminescence decay dynamics. We also discuss the interplay between photon recycling and the photocarriers diffusive transport and demonstrate that at high carrier concentrations, photon recycling dominates the diffusion, conveying the carriers inside the absorbing layer over long distances. We also provide a quantitative determination of a diffusion length that is considerably expanded by the photon recycling process. The effect of the photon recycling process on the Auger recombination rate is also addressed here. The results provide insights for both interpreting the experimental observations and also designing experimental schemes.