Nickel oxide (NiO_x) hole transport layers (HTLs) are desirable contacts for perovskite photovoltaics because they are low cost, stable, and readily scalable; however, they deliver lower open-circuit voltages (V_OCs) compared to organic HTLs. Here, we characterize and mitigate electron transfer-proton transfer reactions between NiO_x HTLs and perovskite precursors. Using XPS and UPS characterization, we identify that Ni^≥3+ metal cation sites in NiO_x thin films act both as Brønsted proton acceptors and Lewis electron acceptors, deprotonating cationic amines and oxidizing iodide species, forming PbI_2−xBr_x-rich hole extraction barriers at the perovskite-NiO_x interface. Titrating reactive Ni^≥3+ surface states with excess A-site cation salts during perovskite active layer deposition yielded an increase in V_OC values to 1.15 V and power conversion efficiencies of ∼20%. This may be a general finding for metal oxide contacts that act as Brønsted and Lewis acid-base reactants toward perovskite precursors, an observation that has also been made recently for TiO₂ and SnO₂ contacts.

氧化镍（NiO _x）空穴传输层（HTL）是钙钛矿光伏产品的理想触点，因为它们成本低，稳定且易于扩展。但是，与有机HTL相比，它们提供的开路电压（V _OC）更低。在这里，我们表征和减轻NiO _x HTL和钙钛矿前体之间的电子转移质子转移反应。通过XPS和UPS表征，我们确定NiO _x薄膜中的^Ni≥3+金属阳离子位点既充当布朗斯台德质子受体和路易斯电子受体，使质子胺去质子并氧化碘化物，形成PbI _2-x Br _x钙钛矿-NiO _x界面处的富孔提取壁垒。在钙钛矿活性层沉积过程中用过量的A-位阳离子盐滴定反应性^Ni≥3+表面态会导致V _OC值增加至1.15 V，功率转换效率约为20％。这对于作为钙钛矿前体的布朗斯台德酸和路易斯酸碱反应物的金属氧化物接触物可能是一个普遍发现，最近也对TiO ₂和SnO ₂接触物进行了观察。