Exploring Organic Metal Halides with Reversible Temperature‐Responsive Dual‐Emissive Photoluminescence

Abstract The exceptional structural tunability of organic metal halides endows them with fascinating electronic and photophysical properties, providing much scope for applications. In this work, single crystals of the organic metal halide (C 4 H 9 NH 3 ) 2 MnI 4 are found to show reversible thermo‐induced luminescent chromism within a wide temperature range. The (C 4 H 9 NH 3 ) 2 MnI 4 single crystal exhibits two emission peaks at 550 and 672 nm, which are assigned to a d–d transition of Mn 2+ ‐centered tetrahedra and self‐trapped excitons, respectively. The temperature‐dependent emission color change is attributed to the thermo‐induced trapping and detrapping process of the self‐trapped exciton. (C 4 H 9 NH 3 ) 2 MnI 4 exhibits a maximum photoluminescence quantum efficiency of up to 68 % at 70 °C. The disclosed interacted photoluminescence decay mechanisms may prove useful for the further design of organic metal halides for optical thermometry.