Controllable deposition of TiO2 nanopillars at room temperature for high performance perovskite solar cells with suppressed hysteresis

A room temperature stratagy was proposed and realized for the fabrication of TiO2 scaffold for perovskite solar cells (PSCs). By sueccetively sputtering TiO2, thermal evaporating PTFE template and sputtering TiO2 again, bilayer TiO2 electron extraction layer was prepared with controllable porosity. Owning to the high sputtering power, the electron transport layer consisting of compact layer and TiO2 nanopillars was fully crystallized and no post thermal treatment was needed for the removal of PTFE template. The hysteresis of PSC was modulated and the porosity dependence of hysteresis was analyzed. PSC with a PCE of 15.08% and neglectable hysteresis was fabricated when the porosity of mesoporous scaffold was 45.77%. Our methodology offered a low cost room temperature scheme for the fabrication of mesostructured PSC. This approach makes large scale flexible PCS devices possible. What is more, this technique is versatile for the preparation of functional mesoporous materials with different pore structure and porosity requirements.