Improvement in the Performance of Inverted 3D/2D Perovskite Solar Cells by Ambient Exposure

Perovskite solar cells (PSCs) are known to be sensitive to the exposure to ambient humidity, which typically results in the degradation and deterioration of performance, although positive effects of exposure to moisture have also been reported, due to recrystallization of the perovskite. Common approach to improve stability is to use 3D/2D perovskite active layer, where 2D capping layer is prepared by spin coating the bulky organic cation halide. Herein, it is shown that optimizing the exposure of the capping layer prepared by spin coating phenylethylammonium iodide (PEAI) to ambient atmosphere results in substantial improvement of the PSC performance. Furthermore, the initial effects of PEAI treatment are dependent on the NiOx/perovskite interface, but in all cases except at very high humidity (80–85% RH) optimized exposure to ambient results in improved performance. The variations in device performance with PEAI treatment and ambient exposure can be attributed to defect passivation and changes in the charge extraction due to energy-level alignment at the interfaces. The best performing devices have passivation of NiOx/perovskite interface and PEAI treatment of top surface followed by exposure to ambient atmosphere at RH of 40–45%, which results in the power conversion efficiency increase from 20.3% to 22.4%.