Vacuum deposited PbI2 film grown at elevated temperatures for improved efficiency of CH3NH3PbI3 based planar perovskite solar cells

Abstract Herein, we report on the elevated temperature vacuum deposition of PbI2 film and its conversion into high-quality CH3NH3PbI3 perovskite film using a two-step vapor-solution deposition process for perovskite solar cells. The CH3NH3PbI3 perovskite films made with PbI2 layer deposited at elevated temperature possess large grain size and pinhole-free morphology, and they exhibit very high absorption and low radiative recombination. We fabricated FTO/PEDOT:PSS/CH3NH3PbI3/PCBM/Al planar perovskite solar cells using PbI2 layers deposited at different substrate temperatures. Interestingly, we observed a major improvement (∼65 %) in the power conversion efficiency of the cell using the perovskite film grown with PbI2 film deposited at 150 °C as compared to the film grown at room temperature. These devices show enhanced ambient stability compared to the case of the PbI2 layer deposited at room temperature. The origin of highly improved performance and higher stability of the devices made with elevated temperature deposition is investigated in detail.