Colloidal lead-free perovskiten anocrystals have recently received extensive attention because of their facile synthesis,t he outstanding size-tunable optoelectronic properties,and less or no toxicity in their commercial applications. Tin(Sn) has so far led to the most efficient lead-free solar cells, yet showing highly unstable characteristics in ambient conditions.H ere,w ep ropose the synthesis of all-inorganic mixture Sn-Ge perovskite nanocrystals,demonstrating the role of Ge 2+ in stabilizing Sn 2+ cation while enhancing the optical and photophysical properties.The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies,reducing the surface traps and leading to alonger excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn-Ge nanocrystals-based devices showthe highest efficiency of 4.9 %, enhanced by nearly 60 %compared to that of pure Sn nanocrystals-based devices.