Universal Elaboration of Al-Doped TiO₂ as an Electron Extraction Layer in Inorganic–Organic Hybrid Perovskite and Organic Solar Cells

Fabricating an electron extraction layer (EEL) with a metal doping transition metal oxide (TMO) in inorganic–organic hybrid perovskite solar cells (PeSCs) and organic solar cells (OSCs) is a simple and efficient process for enhancing photovoltaic properties. Here, the universal benefits and common factors that influence both PeSCs and OSCs as a result of changes in Al-doped TiO₂ properties are investigated. These common factors are identified in two separate mechanisms. The first involves surface smoothing of TiO₂ films, which affects the formation of a high crystalline active layer and reduces recombination between the electron extraction and active layers. The second involves bandgap widening of TiO₂, which reduces the activation energy and enhances the quenching efficiency of devices. These factors are demonstrated in various measurements. The results will help in understanding the fundamental benefits of Al-doped TiO₂ in solution-processed thin-film solar cells.