Nb-doped amorphous titanium oxide compact layer for formamidinium-based high efficiency perovskite solar cells by low-temperature fabrication

Abstract

Low-temperature processed perovskite solar cells (PSCs) were prepared using an amorphous niobium-doped titanium oxide (Nb/TiO_x) film as a compact layer (CL) combined with a brookite TiO₂ mesoporous layer. Nb concentration of 4% in amorphous TiO_x CL was found to improve the photocurrent-voltage performances of formamidinium (FA) and methylammonium (MA)-mixed perovskite, (FAPbI₃)_0.85(MAPbBr₃)_0.15, and FA_0.85Cs_0.15PbI₃ perovskite solar cells, which were fabricated on 100 °C and 130 °C-annealed TiO_x CLs; these solar cells exhibited conversion efficiencies up to 19.1% and 19.8%, respectively. The Nb/TiO_x-based FA_0.85Cs_0.15PbI₃ perovskite cell obtained entirely by a low temperature process (130 °C or less) exhibited high stability against light soaking without encapsulation of the device.