Improvement Performance of Planar Perovskite Solar Cells by Bulk and Surface Defect Passivation

The photovoltaic property of perovskite solar cells (PSCs) is affected by detrimental defects located at the bulk and surface of perovskite films. Furthermore, defect passivation of the perovskite films is challenging. Herein, we add solid CsCl to PbI2 precursor solutions to adjust the properties of PbI2 membranes and obtain perovskite layers with a micrometer-sized grain by reducing grain boundary defects. Bulk defects are reduced by the increase in grain size and decrease in grain boundaries. Fewer bulk defects and the incorporation of Cs increase the device performance, improving the power conversion efficiency (PCE) from 19.72% to 22.24% and suppressing hysteresis. The passivation of surface defects further increases the PCEs and open-circuit voltages (VOC) of PSCs. Therefore, we use 4-methoxyphenethylamine (CH3O–PEAI) to modify the CsCl perovskite films to eliminate the surface defects and suppress nonradiative charge recombination. The surface defect passivation using CH3O–PEAI further improves the PCE of the PSCs to 23.25% with a VOC of 1.186 V, resulting in more efficient and stable PSCs.