Temperature-dependent luminescence in pure and In+-Activated Cs3Cu2I5 single crystals

We report our investigation of the low-temperature optical properties of high-quality Cs2Cu3I5:In+ perovskite single crystals grown by the vertical Bridgman technique. Temperature-dependent radioluminescence in the range 15–300K reveals two main emissions for In+ doped samples at ∼450 nm and the other at ∼620 nm assigned to self-trapping exciton and In+ emissions respectively. Wavelength-resolved thermoluminescence reveals that In+ emission centers are the preferred recombination center for trapped charges. Further investigation of photoluminescence emission/excitation maps reveals a complex electronic structure that arises from spin-orbit coupling-related transitions in In+ and is only observable at low temperatures. Temperature-dependent photoluminescence decay measurements reveal some instances of charge transfer between the self-trapped excitons and In+ ions, as well as some thermally-assisted radiative recombination processes.