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.