Composition-dependent emission linewidth broadening in lead bromide perovskite (APbBr₃, A = Cs and CH₃NH₃) nanoparticles

Lead halide perovskite nanoparticles (NPs) are attractive as they exhibit excellent color purity and have a tunable band gap, and can thus be applied in highly efficient photovoltaic and light-emitting diodes. Fundamental studies of emission linewidth broadening due to spectral shifts in perovskite NPs may suggest a way to improve their color purity. However, the carrier-induced Stark shift that causes spectral diffusion still requires investigation. In this study, we explore composition-related emission linewidth broadening by comparing CsPbBr₃ and CH₃NH₃PbBr₃ (MAPbBr₃) perovskite NPs. We find that the MAPbBr₃ NPs are more sensitive to fluctuations in the local electric fields than the CsPbBr₃ NPs due to an intrinsic difference in the dipole moment between the two A cations (Cs and MA), which shows a carrier-induced Stark shift. The results indicate that the compositions of perovskite NPs are closely associated with emission linewidth broadening and they also provide insights into the development of NP-based devices with high color purity.