Interface Defects Passivation and Conductivity Improvement in Planar Perovskite Solar Cells Using Na<sub>2</sub>S-Doped Compact TiO<sub>2</sub> Electron Transport Layers
Hao Sun, Danyan Xie, Zhen Song, Chuanhui Liang, Lingbo Xu, Xianlin Qu, Yuxin Yao, Deng Li, Hang Zhai, Kun Zheng, Can Cui, Yiying Zhao
Abstract
Numerous trap states and low conductivity of compact TiO2 layers are major obstacles for achieving high power conversion efficiency and high-stability perovskite solar cells. Here we report an effective Na2S-doped TiO2 layer, which can improve the conductivity of TiO2 layers, the contact of the TiO2/perovskite interface, and the crystallinity of perovskite layers. Comprehensive investigations demonstrate that Na cations increase the conductivity of TiO2 layers while S anions change the wettability of TiO2 layers, thus improving the crystallinity of perovskite layers and passivate defects at the TiO2/PVK interface. The synergetic effects of dopants lead to a champion efficiency as high as 21.25% in unencapsulated perovskite solar cells (PSCs), with much-improved stability. Our work provides new insights on anion dopants in TiO2 layers, which is usually neglected in previous reports, and also proposes a simple approach to produce low-cost and high-performance electron transport layers for high-performance PSCs.