摘要：SummaryThe failure of perovskite solar cells (PSCs) under ultraviolet (UV) irradiation is a serious barrier of commercial utilization. Here, a two-stage degradation process of TiO2-based PSCs is discovered under continuous UV irradiation in an inert atmosphere. In the first decay stage, oxygen vacancy-Ti3+(Ti3+-VO) transform into active Ti4+-VOtrap states under UV excitation and cause photocarrier loss. Furthermore, Ti4+-VOstates can convert back into Ti3+-VOstates through oxidizing I−, which result in the accumulation of I3−. Sequentially, the rapid decomposition of perovskite accelerated by increasing I3−replaces the photocarrier loss as the dominant mechanism leading to the second decay stage. Then, a universal method is proposed to improve the UV stability by blocking the transformation of Ti3+-VOstates, which can be realized by polyethyleneimine ethoxylated (PEIE) modified layer. The optimized devices remain ∼75% of its initial efficiency (20.51%) under UV irradiation at 72 days, whereas the normal devices fail completely.Graphical AbstractDisplay OmittedHighlights•A two-stage degradation process of TiO2-based PSCs under continuous UV irradiation•The transformation of Ti3+-VOto Ti4+-VOstates is responsible for the UV degradation•A universal method to enhance the UV stability of PSCs was proposedInorganic Materials; Optical Materials; Materials Chemistry
