Interface\nDefects Passivation and Conductivity Improvement\nin Planar Perovskite Solar Cells Using Na₂S‑Doped\nCompact TiO₂ Electron Transport Layers

Abstract

Numerous\ntrap states and low conductivity of compact TiO₂ layers\nare major obstacles for achieving high power conversion efficiency\nand high-stability perovskite solar cells. Here we report an effective\nNa₂S-doped TiO₂ layer, which can improve the\nconductivity of TiO₂ layers, the contact of the TiO₂/perovskite interface, and the crystallinity of perovskite\nlayers. Comprehensive investigations demonstrate that Na cations increase\nthe conductivity of TiO₂ layers while S anions change the\nwettability of TiO₂ layers, thus improving the crystallinity\nof perovskite layers and passivate defects at the TiO₂/PVK\ninterface. The synergetic effects of dopants lead to a champion efficiency\nas high as 21.25% in unencapsulated perovskite solar cells (PSCs),\nwith much-improved stability. Our work provides new insights on anion\ndopants in TiO₂ layers, which is usually neglected in previous\nreports, and also proposes a simple approach to produce low-cost and\nhigh-performance electron transport layers for high-performance PSCs.