Surface Property\nRegulation of a Magnetron-Sputtered\nNiO<sub><i>x</i></sub> Hole Transport Layer for High-Performance\nInverted Perovskite Solar Cells

The inverted perovskite solar cells (PSCs) are gaining\nincreasing\nattention recently for their unprecedented advantages, such as better\nintegration with tandem and flexible designs, negligible hysteresis,\ngood operational stability, and compatibility with commercially scalable\nfabrication approaches. Nickel oxide (NiOx) films prepared by magnetron\nsputtering technology exhibit excellent scalability and reproducibility,\nwhich could well meet the requirements of the large-scale production\nof inverted PSCs. However, NiOx prepared by vacuum methods generally\nhas fewer surface hydroxyl groups, deteriorating the wettability and\ndamaging the interface contact with the perovskite. Particularly,\nthe Ni<sup>3+</sup> defects on the NiOx surface could lead to unfavorable\nredox reactions with organic cations in the perovskite under high\ntemperatures, promoting the rapid degradation of the perovskite. Thus,\nsurface regulation of sputtered NiOx is imperative for high-performance\nPSCs. Herein, 4-(trifluoromethyl) phenylcarbamate hydrochloride (TFFA)\nwas used to regulate the surface properties of sputtered NiOx. The\nstrongly electronegative F ions in TFFA passivated the Ni<sup>3+</sup> defects on the NiOx surface, suppressed unfavorable interface reactions,\nand improved charge recombination. The polar ammonium functional group\nwas used to adjust the surface energy of NiOx, thereby improving the\nwettability and optimizing the crystallization kinetics of the perovskite.\nAs a result, the power conversion efficiency (PCE) of PSCs reached\n22.76%, which was among the highest PCEs reported for sputtered NiOx-based\ninverted PSCs to date. Moreover, the unencapsulated target devices\nexhibited better stability, maintaining over 85% of the initial PCE\nafter aging for approximately 1200 h in a N<sub>2</sub> environment.\nOur achievements pointed out a practical strategy for enhancing the\nperformance of sputtered NiOx-based inverted PSCs, which could potentially\naccelerate the development and application of large-area PSCs.