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 poreforming 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 re-duces 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.