Mitigating Surface Deficiencies of Perovskite Single Crystals Enables Efficient Solar Cells with Enhanced Moisture and Reverse-Bias Stability

摘要

Metal halide perovskite single crystals are promising for diverse optoelectronicapplications due to their outstanding properties. In comparison to the bulk,the crystal surface suffers from high defect density and is moisture sensitive;however, surface modification strategies of perovskite single crystals are relativelydeficient. Herein, solar cells based on methylammonium lead triiodide(MAPbI_3) thin single crystals are selected as a prototype to improve singlecrystalperovskite devices by surface modification. The surface trap passivationand protection against moisture of MAPbI_3 thin single crystals are achieved byone bifunctional molecule 3-mercaptopropyl(dimethoxy)methylsilane (MDMS).The sulfur atom of MDMS can coordinate with bare Pb~(2+) of MAPbI_3 singlecrystals to reduce surface defect density and nonradiative recombination. Asa result, the modified devices show a remarkable efficiency of 22.2, whichis the highest value for single-crystal MAPbI_3 solar cells. Moreover, MDMSmodification mitigates surface ion migration, leading to enhanced reverse-biasstability. Finally, the cross-link of silane molecules forms a protective layer onthe crystal surface, which results in enhanced moisture stability of both materialsand devices. This work provides an effective way for surface modificationof perovskite single crystals, which is important for improving the performanceof single-crystal perovskite solar cells, photodetectors, X-ray detectors, etc.