Enhanced electronic transport in Fe³⁺-doped TiO₂ for high efficiency perovskite solar cells

Oxygen vacancies in non-stoichiometric TiO₂ electron transport layers can capture injected electrons and act as recombination centers. In this study, the compact TiO₂ electron transport layers of perovskite solar cells (PSCs) are doped with different molar ratios of Fe³⁺ in order to passivate such defects and improve their electron transport properties. The electrical conductivity, absorption, crystal structure, and the performance of the PSCs are systematically studied. It shows that Fe³⁺-doping improves the conductivity of TiO₂ compact layers compared with the pristine TiO₂, boosting the photovoltaic performance of PSCs. The reduced trap-filled limit voltage (V_TFL) of the Fe³⁺-doped TiO₂ compact layers suggests that trap density in the Fe³⁺-TiO₂ films is much lower than that of a pristine TiO₂ film. With the optimized doping concentration (1 mol%) of Fe³⁺, the best power conversion efficiency of PSCs is improved from 16.02% to 18.60%.