Ultraviolet filtration and defect passivation for efficient and photostable CsPbBr3 perovskite solar cells by interface engineering with ultraviolet absorber.

Through reducing the transmission of UV light and suppressing charge recombination, UV-360 as interface modifier helps the CsPbBr 3 PSCs achieve a champion PCE of 9.61% and excellent photostability and moisture-heat tolerance. • The irradiation of UV light on perovskite is filtrated by modifying UV-360. • The defects and the charge recombination of PSCs with UV-360 are markedly reduced. • A large-grained perovskite film is formed on the UV-360 modified TiO 2 ETLs. • A maximum PCE up to 9.61% is achieved for carbon-based CsPbBr 3 PSCs with UV-360. • The unsealed device shows excellent photostability and moisture-heat tolerance. The limited ultraviolet (UV) absorption of the common TiO 2 electron-transporting layers (ETLs) and the trap states density as well as imperfect contact at TiO 2 /perovskite interface have been proposed as one of the main obstacles for realizing long-term photostability and high power conversion efficiency (PCE) of perovskite solar cells (PSCs). To address this issue, an advanced and universal interface engineering has been employed to block UV irradiation on perovskite films and to improve the interface contact with perovskite layer as well as decrease the trap states of TiO 2 via chemical bonding by modifying an efficient UV absorber of 2,2′-methylenebis (4-tert-octyl-6-benzotriazole phenol) (UV-360) on the TiO 2 ETLs. Additionally, the triazole groups in UV-360 combine with the uncoordinated cations of perovskite to reduce the defects at TiO 2 /perovskite interface, and a large-grained perovskite film with low grain boundaries is also formed on the UV-360 modified TiO 2 ETLs owing to the reduction of perovskite nucleation sites. As a result, the modification of UV-360 on TiO 2 greatly filtrates the UV attack on perovskite photosensitive layer and suppresses the interfacial charge recombination as well as promotes charge extraction. Finally, the carbon-based CsPbBr 3 PSC tailored wtih UV-360 modified TiO 2 ETLs free of encapsulation achieves a champion PCE up to 9.61% with super-stability under long-term light soaking as well as UV illumination, high temperature and high humidity conditions in air. Our work provides a new perspective to achieve PSCs wih high efficiency and stability by introducing UV-absorption functional materials. [ABSTRACT FROM AUTHOR]