Efficient perovskite solar cells with low J-V hysteretic behavior based on mesoporous Sn-doped TiO₂ electron extraction layer

Organic-inorganic halide perovskite solar cells (PSCs) have recently become a promising and potentially commercially-ready photovoltaic device. However, the hysteresis effect is one of the most significant problems hindering this progress. The main reasons can be attributed to the lower electron mobility of TiO₂, causing the imbalance of electron and hole flux. The shallow trap states close to the conduction band are formed by oxygen vacancy, leading to charge recombination. Therefore, elements doping is a valuable strategy for improving electron properties and passivating defects. Herein, we proposed Sn as a dopant in mesoporous structure TiO₂ (meso-Sn:TiO₂), causing the conduction band minimum and valence band maximum to be slightly upward shifted. The defect states decreased, and the carrier extraction improved. The PSCs with meso-Sn:TiO₂ electron extraction layer improved the power conversion efficiency from 16.86% to 20.55%, enhanced the fill factor from 76.62% to 81.72%, and reduced hysteresis index from 0.16 to 0.03. This study proves that the Sn dopant is an effective strategy to improve the photovoltaic performance of PSCs.