Besides widely used surface passivation, engineering the film crystallization is an important and more fundamental route to improve the performance of all-inorganic perovskite solar cells. Herein, we have developed a urea-ammonium thiocyanate (UAT) molten salt modification strategy to fully release and exploit coordination activities of SCN- to deposit high-quality CsPbI3 film for efficient and stable all-inorganic solar cells. The UAT is derived by the hydrogen bond interactions between urea and NH4 + from NH4 SCN. With the UAT, the crystal quality of the CsPbI3 film has been significantly improved and a long single-exponential charge recombination lifetime of over 30 ns has been achieved. With these benefits, the cell efficiency has been promoted to over 20 % (steady-state efficiency of 19.2 %) with excellent operational stability over 1000 h. These results demonstrate a promising development route of the CsPbI3 related photoelectric devices.
Keywords: all-inorganic perovskites; cesium lead triiodide; molten salts; solar cell; thiocyanate.
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