Replacing PbI2 by MAPbI3 to Realize Large Grain Size and Reduced Hysteresis for Highly Efficient Perovskite Solar Cells

Depositing high-quality perovskite film is of great importance to achieve efficient perovskite solar cells. In this work, we develop an improved precursor solution by directly mixing MAPbI(3), PbCl2, and MAI. Different from the conventional one-step solution processing method, in which MAPbI(3) is in situ generated from the reaction of PbI2 and MAI, in our case, pure MAPbI(3) from commercial source is applied. The MAPbI(3):PbCl2:MAI precursor results in improved perovskite film morphology with large grain sizes, as well as enhanced charge transportation process. In addition, reduced hysteresis of the corresponding device is observed compared to the control device using PbI2:PbCl2: MAI precursor. Planar perovskite solar cell prepared from MAPbI(3)-based precursor exhibits a champion efficiency of 18.70%, with V-oc of 1063 mV, J(sc) of 21.91 mA cm(-2), and FF of 80%. In contrast, control device shows a moderate PCE of 16.71% under the same condition. The pure MAPbI(3) introduced is favorable as perovskite crystallite domains, and the high-quality perovskite films formed lead to enhanced photovoltaic performances.