All‐Inorganic Lead‐Free 0D Perovskites by a Doping Strategy to Achieve a PLQY Boost from <2 % to 90 %

Abstract Zero‐dimensional (0D) lead‐free perovskites have unique structures and optoelectronic properties. Undoped and Sb‐doped all inorganic, lead‐free, 0D perovskite single crystals A 2 InCl 5 (H 2 O) (A=Rb, Cs) are presented that exhibit greatly enhanced yellow emission. To study the effect of coordination H 2 O, Sb‐doped A 3 InCl 6 (A=Rb, Cs) are also synthesized and further studied. The photoluminescence (PL) color changes from yellow to green emission. Interestingly, the photoluminescence quantum yield (PLQY) realizes a great boost from <2 % to 85–95 % through doping Sb 3+ . We further explore the effect of Sb 3+ dopants and the origin of bright emission by ultrafast transient absorption techniques. Furthermore, Sb‐doped 0D rubidium indium chloride perovskites show excellent stability. These findings not only provide a way to design a set of new high‐performance 0D lead‐free perovskites, but also reveal the relationship between structure and PL properties.