Temperature-dependent self-trapped exciton emission in Cu(I) doped zinc-based metal halides from well-resolved excited state structures

Zero-dimensional metal halides are of unique structures and tunable photoluminescence properties, showing great potential applications such as light-emitting diodes (LEDs) and sensing. Herein, we successfully synthesized Cu + doped (MA) 2 ZnCl 4 metal halides by a slow evaporation solvent method. The introduction of Cu + results in sky-blue self-trapped exciton emission in (MA) 2 ZnCl 4 at 486 nm at room temperature, and a photoluminescence quantum yield is as high as 54.9%. Interestingly, at low temperatures, Cu + -doped (MA) 2 ZnCl 4 exhibits two emission peaks located at 482 and 605 nm, respectively. This temperature-dependent dual emission indicates two excited state structures that exist on the triplet excited-state potential energy surface. In addition, the temperature sensor we fitted has good performance ( S r = 1.65 %·K −1 ), which is the first attempt in Cu + doped Zn-based metal halides. Our work enriches the family of sky-blue metal halides and provides a promising strategy for building sky-blue LEDs.