UV-robust and efficient perovskite solar cells enabled by interfacial photocatalysis suppression and defect passivation

Abstract

The interfacial photocatalysis of metal oxide electron transport layers (ETLs), especially TiO₂, in organometal halide perovskite solar cells (PSCs) has detrimental effects on device stability. Herein, a UV absorber, 4,4′-oxybisbenzoic acid (OBBA), was first utilized as a modification layer between TiO₂ and perovskite against UV photocatalytic degradation. Owing to the strong UV filtration capability and coordination effect of OBBA molecules, the harmful UV light was filtered and the oxygen vacancies on the TiO₂ surface were eliminated, which significantly suppressed the interfacial photocatalysis reaction, and the photocatalytic degradation mechanism of perovskite under UV irradiation was proposed for the first time. Moreover, the uncoordinated Pb²⁺ defects at the buried interface were passivated and the energy band alignment was optimized. Consequently, the modified device presented a high power conversion efficiency (PCE) of up to 22.14% and excellent stability under extreme UV irradiation (365 nm, 600 mW cm⁻²; 275 nm, 10 mW cm⁻²).