Hydroxyl-functionalized ultrathin NiOx interlayer for minimized energy loss and enhanced interface stability in perovskite photovoltaics

Self-assembled monolayers (SAMs) have significantly advanced perovskite-based photovoltaics by suppressing interfacial energy loss, yet their performance is limited by poor adsorption at the underlying substrates. Herein, we developed a water-mediated atomic layer deposition (ALD) process for ultrathin (∼3 nm) NiO_x films at low temperatures, simultaneously eliminating the need for oxygen/ozone precursors and high-temperature post-annealing typically required in conventional approaches. Meanwhile, the NiO_x films exhibit a high density of chemically adsorbed hydroxyl groups while minimizing the presence of detrimental Ni species. These properties enhance the uniformity and stability of SAMs and facilitate high-quality perovskite crystallization, thereby effectively suppressing nonradiative recombination at the buried interface for more effective hole extraction. Consequently, the 1.67 eV perovskite solar cells and perovskite/silicon tandem solar cells (TSCs) exhibit power conversion efficiencies of 23.20% and 30.38%, respectively, accompanied by outstanding stability under conditions of humidity, elevated temperature, and illumination. This work establishes a scalable and cost-effective ALD strategy, paving the way for the commercialization of high-performance and durable perovskite/silicon TSCs.