Perovskite solar cells (PSCs) with inverted structures have received significant attention in the field of photovoltaics. NiO is one of the commonly explored hole transport materials (HTMs) because of its excellent chemical stability in comparison with organic materials. Pure NiO is an insulator, but the presence of nickel vacancies can lead to the formation of Ni³⁺ ions, resulting in p-type semiconductor properties. However, the low conductivity and poor interfacial contact between NiO and perovskite thin films still pose challenges in achieving high-performance inverted PSCs. To solve these problems, potassium acetate is used as a potassium source for a nickel precursor, and therefore potassium ions (K⁺) are doped into NiO nanocrystals. The introduction of K⁺ into NiO leads to the formation of Ni³⁺ ions, thereby increasing the conductivity and hole mobility of NiO. Furthermore, K⁺-doped NiO exhibits better interface contact with the perovskite film, facilitating the efficient separation of photo-generated charges and showing a strong photoluminescence quenching effect. Experimental results demonstrate that the optimal concentration of K⁺ doping is 3%, and the PSCs prepared with K⁺-doped NiO exhibit a significant increase in efficiency, from 15.15% to 16.75%, which is attributed primarily to the improvements in the short-circuit current density and fill factor. These improvements highlight the importance of enhanced conductivity and better interfacial contact achieved through K⁺ doping for charge carrier collection, effectively addressing the limitations of NiO in inverted PSCs.