Disentangling Dual Emission Dynamics in Lead Bromide Perovskite

Metal halide perovskites exhibit intriguing properties for optoelectronic and electronic applications. Understanding their intrinsic photoexcitation and band-tail dynamics is essential for exploring novel functionality and improving device performance. This report addresses the band-tail luminescence of lead bromide perovskite (APbBr₃) single crystals, where A is methylammonium, formamidinium, and cesium. Using time-resolved photoluminescence (PL) spectroscopy, the dynamics of well-defined dual emission peaks are unambiguously resolved from the picosecond to the microsecond scale. Whereas the long-lived states exhibit similar recombination dynamics at high temperatures, a clear, fast transition occurs between the high and low energy states at low temperatures, indicating direct communication between these two states. These time-resolved PL spectra shed light on the intrinsic optical properties of metal halide perovskites.