Efficient two-step sequential deposition perovskite solar cells via PbCl2 enhanced PbI2 precursor

Two-step sequentially deposited FAPbI3 polycrystalline film is adopted to produce high-performance perovskite solar cells (PSCs) with outstanding power conversion efficiency (PCE). The pore-forming of the inorganic film is beneficial to the second organic salt infiltrate, thus promoting a solid-solution reaction. Here, lead chloride (PbCl2) is introduced into lead iodide (PbI2) precursor solution to adjust the properties of PbI2 membranes and obtain a micrometer-sized perovskite layer by reducing grain boundary defects. The incorporation of PbCl2 reduces bulk defects and improves the device's performance. The PSCs displayed good operational stability in the dry atmosphere over 2 months. The PCE of PSCs exhibited an increased trend in the initial measurement and then showed decreased trend. A champion PCE of 22.07% was obtained after storage. Furthermore, the PL/TRPL of perovskite film and perovskite/Spiro-OMeTAD interface was tested to explain the efficiency evolution. This work may provide a strategy for further improving the performance of PSCs via fine-controlled PbI2 membranes in the perovskite layer.