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 (CsPbI₃) perovskite thin films via alternate vacuum deposition. We also investigated the effect of layer-by-layer deposition of PbI₂/CsI to fabricate efficient planar heterojunction CsPbI₃ thin films and solar cells. This procedure is comparatively simple when compared with commonly used coevaporation techniques; further, precise intercalation control of the CsPbI₃ thin films can be achieved by increasing the number of layers in the layer-by-layer deposition of PbI₂/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 CsPbI₃ 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 (<i>J</i>_sc) of 12.06 mA/cm², an open-circuit voltage (<i>V</i>_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