Bimolecular Passivation Layer Modified NiO _<i>x</i> to Improve the Efficiency and Stability of Perovskite Solar Cells

NiO_<i>x</i> as a hole transport layer (HTL) for inverted perovskite solar cells (PSCs) shows significant commercialization prospects for enhancing device efficiency. However, limited by the problem of defects at the interface between perovskite and NiO_<i>x</i>, achieving effective interfacial passivation still faces many challenges. In this study, Me-4PACz is doped with potassium 4-chlorophenyl trifluoroborate (PCPTFB) to form a co-self-assembled monolayer (Co-SAM) to modify the buried interface of PSCs. The system effectively passivates NiO_<i>x</i> surface defects by PCPTFB, optimizes the Ni³⁺/Ni²⁺ ratio, enhances the hole extraction capability, and improves the energy band matching. In addition, PCPTFB synergistically stabilized the perovskite interface, reduced nonradiative recombination, and promoted the formation of high-quality perovskite films. Based on the above optimization, the Me-4PACz+PCPTFB modified device achieved an excellent photoelectric conversion efficiency (PCE) of 23.68%. For the stability test, the unencapsulated PSCs maintained an initial efficiency of 90% after 1400 h of aging in a nitrogen environment, demonstrating excellent long-term stability. This innovative strategy not only highlights the important role of Me-4PACz+PCPTFB in NiO_<i>x</i>/perovskite interfacial engineering but also provides a new technological path to realize efficient and stable PSCs.