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UV degradation mechanism of TiO2-based perovskite solar cells studied by pump-probe spectroscopy
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2020
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In this study, the microscopic carrier dynamics that govern the UV stability of perovskite solar cells was investigated using pump-probe spectroscopy. In conventional perovskite solar cells, the UV-active oxygen vacancy in compact TiO<sub>2</sub> prohibits current generation after UV degradation. On the other hand, the dominant vacancy type in 2D Ti<sub>1-x</sub>O<sub>2</sub> atomic sheet transporting layer (ASTL) is a titanium vacancy, not UV-sensitive. Consequently, the carrier recombination are suppressed and further extends UV stability in perovskite solar cells with a 2D Ti<sub>1-x</sub>O<sub>2</sub> ASTL. The dynamics of electron diffusion, electron injection, and hot hole transfer processes are found to be less sensitive to the UV irradiation. The ultrafast time-resolved data shown here clearly represent a close correlation between the carrier dynamics and UV aging of perovskite, thus providing insight into the origin of UV-induced degradation in perovskite solar cells.