Controlled NiO x Defect Engineering to Harnessing Redox Reactions in Perovskite Photovoltaic Cells via Atomic Layer Deposition.

Albeit the undesirable attributes of NiO x , such as low conductivity, unmanageable defects, and redox reactions occurring at the perovskite/NiO x interface, which impede the progress in inverted perovskite solar cells (i-PSCs), it is the most favorable choice of technology for industrialization of PSCs. In this study, we propose a novel Ni vacancy defect modulate approach to leverage the conformal growth and surface self-limiting reaction characteristics of the atomic layer deposition (ALD)-fabricated NiO x by varying the O 2 plasma injection time ( t OE ) to induce self-doping. Consequently, NiO x thin films with enhanced conductivity, an appropriate Ni 3+ /Ni 2+ ratio, stable surface states, and ultrathinness are realized as hole-transporting layers (HTLs) in p-i-n PSCs. As a result of these improvements, ALD-NiO x -based devices exhibit the highest power conversion efficiency (PCE) of 19.86% and a fill factor (FF) of 81.86%. Notably, the optimal interfacial defects effectively suppressed the severe reaction between the perovskite and NiO x . This suppression is evidenced by the lowest decay rate observed in a harsh environment, lasting for 500 consecutive hours. The proposed approach introduces the possibility of a hierarchical distribution of defects and offers feasibility for the fabrication of large-area, uniform, and high-quality films.