Co-Self-Assembled Monolayers Modified NiO<i>_X</i>/Perovskite Interface for High-Performance Wide Bandgap Perovskite Solar Cells

Wide bandgap (WBG) NiOX-based perovskite solar cells demonstrate significant potential for achieving efficient and stable perovskite/silicon tandem solar cells. Nevertheless, the enhancement of device efficiency continues to be constrained by severe interface defects, inadequate hole extraction, and a substantial energy level mismatch between the NiOX hole transport layer (HTLs) and the perovskite layer. Here, we propose an interface engineering strategy involving the mixture of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid and [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid as Co-SAM modified NiOX HTLs. This approach effectively suppresses nonradiative recombination at the HTL/perovskite interface, and the finely optimized energy-level arrangement significantly facilitates hole extraction at the interface. As a result, the 1.68 eV inverted WBG perovskite solar cell with Co-SAM-modified NiOX exhibited an impressive efficiency of 21.6%, with an open-circuit voltage of 1.19 V and a fill factor of 81.2%, as well as excellent long-term stability under one solar illumination. This study provides valuable insights for addressing the challenge of the NiOX/perovskite buried interface and realizing high-performance and durable perovskite cells.