Efficient (>20 %) and Stable All‐Inorganic Cesium Lead Triiodide Solar Cell Enabled by Thiocyanate Molten Salts

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 CsPbI 3 film for efficient and stable all‐inorganic solar cells. The UAT is derived by the hydrogen bond interactions between urea and NH 4 + from NH 4 SCN. With the UAT, the crystal quality of the CsPbI 3 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 CsPbI 3 related photoelectric devices.