High-Performance Inverted Perovskite Solar Cells with Sol–Gel-Processed Sliver-Doped NiO_X Hole Transporting Layer

Nickel oxide (NiO_X) has been established as a highly efficient and stable hole-transporting layer (HTL) in perovskite solar cells (PSCs). However, existing deposition methods for NiO_X have been restricted by high-vacuum processes and fail to address the energy level mismatch at the NiO_X/perovskite interface, which has impeded the development of PSCs. Accordingly, we explored the application of NiO_X as a hybrid HTL through a sol–gel process, where a NiO_X film was pre-doped with Ag ions, forming a p/p⁺ homojunction in the NiO_X-based inverted PSCs. This innovative approach offers two synergistic advantages, including the enlargement of the built-in electric field for facilitating charge separation, optimizing energy level alignment, and charge transfer efficiency at the interface between the perovskite and HTL. Incorporating this hybrid HTL featuring the p/p⁺ homojunction in the inverted PSCs resulted in a high-power conversion efficiency (PCE) of up to 19.25%, significantly narrowing the efficiency gap compared to traditional n-i-p devices. Furthermore, this innovative strategy for the HTL enhanced the environmental stability to 30 days, maintaining 90% of the initial efficiency.