Sequential hybrid self-assembled monolayers enabling uniform coverage and efficient hole extraction in perovskite photoelectronics

This study demonstrates a sequential hybrid self-assembled monolayer (SH-SAM) strategy that enables stepwise regulation of interfacial coverage and energetic alignment to optimize the buried interface in inverted perovskite solar cells (PSCs). While self-assembled monolayers (SAMs) are essential for hole-selective contacts, achieving simultaneous uniform molecular coverage and precise energy-level alignment remains a significant challenge. To address this issue, we construct a hybrid self-assembled monolayer by sequentially depositing two carbazole-based phosphonic acids. In this architecture, the primary molecular layer regulates substrate wettability and nucleation conditions, whereas the secondary deposition fine-tunes interfacial dipole modification and the work-function. This sequential assembly results in improved surface coverage and more homogeneous interfacial properties, accompanied by a measurable work-function shift. Consequently, perovskite films grown on the modified surface exhibit enlarged grain, reduced trap density, and suppressed non-radiative recombination, which are collectively associated with improved interfacial coverage, energetic homogenization, and suppressed interfacial non-radiative recombination. Thus, devices incorporating SH-SAM reach a power conversion efficiency of 22.1%, with an improved fill factor and enhanced stability under ambient storage conditions. These findings provide a feasible strategy for stepwise regulation of interfacial coverage and energetic alignment at buried interfaces in perovskite photoelectronics