Improved Reproducibility and Intercalation Control of Efficient Planar Inorganic Perovskite Solar Cells by Simple Alternate Vacuum Deposition of PbI2 and CsI

Vacuum deposition is a simple and controllable approach that aims to form higher-quality perovskite films compared with those formed using solution-based deposition processes. Herein, we demonstrate a novel method to promote the intercalation control of inorganic cesium lead iodide (CsPbI 3 ) perovskite thin films via alternate vacuum deposition. We also investigated the effect of layer-by-layer deposition of PbI 2 /CsI to fabricate efficient planar heterojunction CsPbI 3 thin films and solar cells. This procedure is comparatively simple when compared with commonly used coevaporation techniques; further, precise intercalation control of the CsPbI 3 thin films can be achieved by increasing the number of layers in the layer-by-layer deposition of PbI 2 /CsI. The best control and the highest reproducibility were achieved for the deposition of four double layers owing to the precise intercalation control during the deposition of the CsPbI 3 thin film. A power conversion efficiency of 6.79% was obtained via alternating vacuum deposition of two double layers with a short-circuit current density ( J sc ) of 12.06 mA/cm 2 , an open-circuit voltage ( V oc ) of 0.79 V, and a fill factor (FF) of 0.72. Our results suggest a route for inorganic precursors to be used for efficient perovskite solar cells via alternating vacuum deposition.