Evaporated Nickel Oxide Films with Slow Annealing and Interface Modification for Perovskite Solar Cells

Electron-beam-evaporated nickel oxide (NiO_x) films are known for their high quality, precise control, and suitability for complex structures in perovskite (PVK) solar cells (PSCs). However, untreated NiO_x films have inherent challenges, such as surface defects, relatively low intrinsic conductivity, and shallow valence band maximum, which seriously restrict the efficiency and stability of the devices. To address these challenges, we employ a dual coordination optimization strategy. The strategy includes low heating rate annealing of NiO_x films and using an aminoguanidine nitrate spin coating process on the surfaces of NiO_x films to strategically modify NiO_x films itself and the interface of NiO_x/PVK. Under the synergistic effect of this dual optimization method, the quality of the films is significantly improved and its p-type characteristics are enhanced. At the same time, the interface defects and energy level alignment of the films are effectively improved, and the charge extraction ability at the interface is improved. The combined treatment significantly improved the efficiency of inverted PSCs, from 17.85% to 20.31%, and enhanced device stability under various conditions. This innovative dual-coordinated optimization strategy provides a clear and effective framework for improving the performance of NiO_x films and inverted PSCs.