Effect of self-trapped excitons in the optical properties of manganese-alloyed hexagonal-phased metal halide perovskite

Emission induced by self-trapped excitons (STEs) has recently been studied in several metal halide perovskites (MHPs), particularly in low-dimensional MHPs. STEs generally occur in low-dimensional MHPs owing to their soft lattices, strong electron–phonon coupling, and lattice distortion. However, the formation of STEs in all-inorganic high-dimensional MHPs, specifically in hexagonal phases, is challenging. From this perspective, we studied the formation of STEs in all-inorganic hexagonal-phase CsCdCl3 MHPs and further investigated the role of free excitons and STEs in the optical properties of CsCd(1-x)MnxCl3 MHPs. Mn2+ ion-activated CsCd(1-x)MnxCl3 MHPs were synthesized, and their crystal structures were refined. The CsCd(1-x)MnxCl3 MHPs exhibited orange emission upon 295 nm excitation with a high photoluminescence quantum yield of 74 %. Moreover, CsCd(1-x)MnxCl3 MHPs exhibited good thermal and chemical stability. We also investigated the effect of Mn2+ doping on CsCd(1-x)MnxCl3 single crystals, polycrystals, and nanocrystals. This work offers deep insights into the photophysical properties of MHPs as well as provides a promising approach to achieving high-quality, thermally, and chemically stable white-light emission.