Temperature-dependent photoluminescence spectra and decay dynamics of MAPbBr₃ and MAPbI₃ thin films

The steady-state spectra and fluorescence lifetimes are investigated under vacuum for methylammonium lead bromide and iodide (CH₃NH₃PbBr₃ or MAPbBr₃, and CH₃NH₃PbI₃ or MAPbI₃) thin films by stably controlling the sample temperature in the range of 78 K to 320 K. The transformation of spectrum features and lifetime components are proved to be quite sensitive to the temperatures in accordance with the phase transition of structures. Our work demonstrates that the halide anions I^- and Br^- lead to remarkable differences on optical characteristics. Due to the distinct behaviors of excitons, electron-hole pairs and free carriers in decay channels, MAPbI₃ has much longer lifetime and higher low-temperature fluorescence efficiency than those of MAPbBr₃. The findings provide possible choices for certain perovskites under various ambient temperature conditions to display photovoltaic or luminescent advantage.