Sputtered nickel oxide (NiOx) has become one of the most promising inorganic hole transport layers for p–i–n perovskite solar cells (PSCs) due to its appealing features such as its robust nature, low material cost, and easy integration to tandem structures and large-area applications. However, the main drawback with NiOx-based PSCs is typically low open-circuit voltage (VOC) due to the inferior energy-level alignment, low charge mobility, and high recombination at the interface. Herein, two types of phosphonic acid self-assembled monolayers (SAMs) deposited by blade coating as an interfacial layer to modulate the sputtered NiOx/perovskite interface properties are used. While sputtered NiOx serves as a conformally coated hole selective layer, the ultrathin SAM interlayer facilitates the hole extraction and minimizes the energy loss at the interface. Co-ordinately introduced stabilizing additive, namely octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (I-76), further improves the device performance of NiOx/SAM-based PSCs, resulting in VOC of 1.14 V and a power conversion efficiency of 21.8%. By applying these strategies for perovskite module upscaling, aperture area module efficiencies of 19.7%, 17.5%, and 15.5% for perovskite minimodules of 4, 16, and 100 cm2 are demonstrated, corresponding to active area module efficiencies of 20.4%, 18.0%, and 16.4%, respectively.