Photo-induced degradation of lead halide perovskite solar cells caused by the hole transport layer/metal electrode interface

Abstract

Lead halide perovskite solar cells (PSCs) suffer from poor long-term stability, especially due to photo-induced degradation, as PSCs function under continuous sunlight. However, the origins of this instability have not been clearly explored. Herein, the photo-induced degradation of PSCs with mesoporous and planar architectures are investigated, respectively, and the main origin is proved to be correlated with the hole transport material (HTM)/metal (Au) electrode interface. The solar irradiation of PSCs causes significant deterioration of device performance, with the efficiency decreasing from approximately 18% to 2.46% for planar PSCs in 180 min. Electrical analysis of the PSCs and XPS measurements show that the deteriorated performance is induced by retarded carrier extraction from the HTM to the Au electrode, due to a broken interface binding. Accordingly, in situ renewal of the Au electrode was found to cause notable recovery (approximately 80%) of the device performance of both mesoporous and planar PSCs. In comparison, the material degradation of perovskite and the TiO₂/perovskite interface were also studied; however, these showed minor effects on the photo-induced degradation of PSCs. These results indicate that the photo-induced degradation of PSCs is mainly caused by the HTM/Au interface. This study provides an important insight into the photo-induced degradation of PSCs, and is crucial for the fabrication of highly photo-stable PSCs.