Shallow trap mediated temperature-dependent exciton and Mn2+ photoluminescence in CsPbCl3:Mn2+ nanocrystals

As an effective means to endow lead halide perovskite nanocrystals (NCs) with new properties, ion doping has been widely applied. Transition metal Mn-doped CsPbCl3 is of particular interest, as the Mn doping introduces new emission bands, improves photoluminescence quantum yield (PLQY), and even enhances stability. However, it is still insufficient to catch insight of the energy transfer process and luminescence characteristics of these high defect tolerance NCs doped with Mn ion. Here, we systematically studied the energy transfer from exciton to Mn2+ ions in Mn-doped CsPbCl3 NCs by variable temperature steady-state fluorescence spectra and time-resolved spectra. The abnormal attenuation behavior of the exciton and Mn2+ with the change of temperature was observed, from which we predict the existence of shallow traps near the conduction band and these shallow traps will affect the luminescence properties by influencing the energy transfer process. We show a simple physical model invoking only shallow trap states that uniquely describe the temperature-dependent energy transfer between the exciton and the Mn2+ ion. The thermometric performance (30–290 K) was studied in terms of relative thermal sensitivity, in which the calculated relative sensitivity range is ∼0.12%–1% K−1.