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

Abstract The limited ultraviolet (UV) absorption of the common TiO2 electron-transporting layers (ETLs) and the trap states density as well as imperfect contact at TiO2/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 TiO2 via chemical bonding by modifying an efficient UV absorber of 2,2′-methylenebis (4-tert-octyl-6-benzotriazole phenol) (UV-360) on the TiO2 ETLs. Additionally, the triazole groups in UV-360 combine with the uncoordinated cations of perovskite to reduce the defects at TiO2/perovskite interface, and a large-grained perovskite film with low grain boundaries is also formed on the UV-360 modified TiO2 ETLs owing to the reduction of perovskite nucleation sites. As a result, the modification of UV-360 on TiO2 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 CsPbBr3 PSC tailored wtih UV-360 modified TiO2 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.