[en] Zero-dimensional (0D) lead-free perovskites have unique structures and optoelectronic properties. Undoped and Sb-doped all inorganic, lead-free, 0D perovskite single crystals $A_{2}InC{l}_5(H_{2}O)$ (A=Rb, Cs) are presented that exhibit greatly enhanced yellow emission. To study the effect of coordination $H_{2}O$, Sb-doped $A_{3}InC{l}_6$ (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 $S{b}^{3+}$. We further explore the effect of $S{b}^{3+}$ 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. (© 2020 Wiley‐VCH Verlag GmbH and Co. KGaA, Weinheim)