Investigation of the Acceleration and Suppression of the Light-Induced Degradation of a Lead Halide Perovskite Solar Cell Using Hard X-ray Photoelectron Spectroscopy

Lead halide perovskite is a candidate for next-generation solar cells. Improvements in photovoltaic conversion efficiency and cell durability in different environments, such as moisture, heat, and light, are pertinent for practical use. Researchers must solve the problem of light-induced degradation (LID) of perovskite solar cells. Oxygen accelerates LID. However, a buffer layer between the electron transport layer (ETL)/perovskite interface suppresses LID. Herein, we report the influence of oxygen and the buffer layer on LID at the perovskite [(FA 0.83 MA 0.17 ) 0.95 Cs 0.05 (I 0.95 Br 0.05 ) 3 with 2.5 mol % RbI additive]/hole transport layer (HTL) and ETL/perovskite interfaces by hard X-ray photoelectron spectroscopy. We confirmed that oxygen accelerated the increase in the fraction of neutral iodine at the perovskite/HTL interface after light illumination and the introduction of a self-assembled monolayer as the buffer layer greatly suppressed the increase in the fraction of neutral lead at the ETL/perovskite interface, suggesting that photoelectrochemical reactions at the interfaces play an important role in the LID of perovskite solar cells.