LAUSR

TiO2 is commonly used to prepare electron transport layers (ETLs) in perovskite solar cells (PSCs). However, conventional TiO2 ETLs suffer from low electron mobility and charge recombination. Here, we report the direct growth of TiO2 ETLs on fluorine doped conductive (FTO) glasses with titanium tetrafluoride (TiF4) as the reactant by hydrothermal method. The TiO2 ETLs have pure anatase phase, single crystal structure and three-dimensional (3D) nanoarrays morphology. This 3D-TiO2 ETLs mainly consist of thermodynamically stable surfaces {101} and more reactive surfaces {001}. Compared with the conventional TiO2 ETLs, the 3D-TiO2 ETLs can effectively optimize energy level matching and charge transfer dynamics. The special morphology of 3D-TiO2 ETLs can well assist to form high quality CsPbIBr2 with larger crystal grains. The champion CsPbIBr2 PSC with 3D-TiO2 ETL achieves an efficiency as high as 10.65%, which is equal to the one with hole-transport and Au electrode structure (10.79%) and much higher than the pristine one (7.16%) with the conventional TiO2 ETL. Furthermore, the 3D-TiO2 ETLs show ultraviolet (UV) shielding function, which can effectively overcome the UV instability defect of conventional TiO2 ETLs and obviously enhance UV stability of CsPbIBr2 and the corresponding PSCs. Therefore, the 3D-TiO2 ETLs can be good candidates for preparing high-efficiency and UV stable carbon-based CsPbIBr2 PSCs.