Luminescence Change from Orange to Blue for Zero‐Dimensional Cs2InCl5(H2O) Metal Halides in Water and a New Post‐doping Method

Zero-dimensional metal halides have attracted much attention due to their attractive photoelectric properties. Here, we propose a new strategy of synthesizing metal halides crystals by recrystallization in water. The as-synthesized Cs2 InCl5 (H2 O)-orange crystals are dissolved and recrystallized in water (Cs2 InCl5 (H2 O)-blue), with its photoluminescence (PL) changing from orange to blue, both of which are derived from self-trapping excitons (STEs). The time-resolved photoluminescence (TRPL) spectrum of Cs2 InCl5 (H2 O)-blue shows that it has an ultralong lifetime up to milliseconds (τ=52.98 ms), which is expected to be applied in biological sensors. The photoluminescence quantum yield (PLQY) increases from 2.25% to 11.61% in the self-assembly process. By using a post-doping method, the PL of crystals turns into red when we introduce Mn2+ as dopant while there is no obvious change upon using a traditional solvent-thermal method. Recrystallization in water and post-doping provide a new perspective for the synthesis and doping of metal halides.