Achieving high-performance planar perovskite solar cell with Nb-doped TiO2 compact layer by enhanced electron injection and efficient charge extraction

Abstract

The power conversion efficiency (PCE) of a planar perovskite solar cell (PSC) is closely associated with the conduction band energy, conductivity and coverage of the compact layer. However, as the most widely used compact layer material, TiO₂ has unfavorable electrical properties such as low electron mobility and conductivity; as a result, modifications such as elemental doping are of paramount importance. In this study, Nb-doped TiO₂ with improved carrier density and conductivity was prepared via a facile one-pot solution process and applied successfully as a high-quality compact layer for planar PSCs. A positive shift in the flat-band potential (V_fb) and increased conductivity after Nb doping efficiently facilitated photogenerated electron injection and charge extraction from the perovskite film to the 2% Nb-doped TiO₂ compact layer, contributing to impressive advances in photovoltaic performance compared with pristine TiO₂. Ultimately, a PSC assembled using optimized 2% Nb-doped TiO₂ and CH₃NH₃PbI₃ yielded a power conversion efficiency of up to 16.3%.