Surface Property Regulation of a Magnetron-Sputtered NiOx Hole Transport Layer for High-Performance Inverted Perovskite Solar Cells

The inverted perovskite solar cells (PSCs) are gaining increasing attention recently for their unprecedented advantages, such as better integration with tandem and flexible designs, negligible hysteresis, good operational stability, and compatibility with commercially scalable fabrication approaches. Nickel oxide (NiOx) films prepared by magnetron sputtering technology exhibit excellent scalability and reproducibility, which could well meet the requirements of the large-scale production of inverted PSCs. However, NiOx prepared by vacuum methods generally has fewer surface hydroxyl groups, deteriorating the wettability and damaging the interface contact with the perovskite. Particularly, the Ni³⁺ defects on the NiOx surface could lead to unfavorable redox reactions with organic cations in the perovskite under high temperatures, promoting the rapid degradation of the perovskite. Thus, surface regulation of sputtered NiOx is imperative for high-performance PSCs. Herein, 4-(trifluoromethyl) phenylcarbamate hydrochloride (TFFA) was used to regulate the surface properties of sputtered NiOx. The strongly electronegative F ions in TFFA passivated the Ni³⁺ defects on the NiOx surface, suppressed unfavorable interface reactions, and improved charge recombination. The polar ammonium functional group was used to adjust the surface energy of NiOx, thereby improving the wettability and optimizing the crystallization kinetics of the perovskite. As a result, the power conversion efficiency (PCE) of PSCs reached 22.76%, which was among the highest PCEs reported for sputtered NiOx-based inverted PSCs to date. Moreover, the unencapsulated target devices exhibited better stability, maintaining over 85% of the initial PCE after aging for approximately 1200 h in a N₂ environment. Our achievements pointed out a practical strategy for enhancing the performance of sputtered NiOx-based inverted PSCs, which could potentially accelerate the development and application of large-area PSCs.