Robust Adsorption of Self-Assembled Monolayer on NiOx via Multiple Hydrogen Bonds for Stable Inverted Perovskite Solar Cells.

Abstract

In inverted perovskite solar cells, self-assembled molecules (SAMs) employed as hole-transport layers can significantly improve device performance, with power conversion efficiencies currently exceeding 27%. However, the non-uniform and weak adsorption of SAMs on metal oxide substrates leads to severe non-radiative recombination at the buried interface, which remains a critical bottleneck for long-term operational and thermal stability. In this study, heptafluorobutyramide (HA) or heptafluorobutylimidamide (HM) is introduced into MeO‑4PACz to tailor its adsorption on the NiO_x surface. Leveraging multiple hydrogen‑bonding interactions between HM and MeO‑4PACz, the resulting SAMs adopt an inclined orientation of approximately 60° relative to the NiO_x surface. This configuration increases the proportion of Ni³ ⁺ on the substrate and raises the surface coverage from 0.912 to 1.236. It also effectively passivates undercoordinated Pb defects at the buried interface, enhances interfacial uniformity, and suppresses non‑radiative recombination. Using a vacuum‑flash processing method, HM‑optimized devices achieve a champion efficiency of 26.99% (certified steady‑state efficiency 26.62%) and reach 20.36% on a large‑area module with an active area of 809.69 cm². Moreover, small-area devices retained 92% and 87% of their initial efficiency after 1500 h of maximum power point tracking at 25°C and 60°C, respectively.