Tailoring Self-Assembled Monolayers with Post-Assembly Nicotinic Acids for Efficient and Ultraviolet Stable Inverted Perovskite Solar Cells

Abstract

While inverted perovskite solar cells (PSCs) based on self-assembly monolayers (SAMs) have achieved record power conversion efficiencies (PCEs), two major challenges remain: incomplete SAM coverage on the substrate and inadequate defect passivation at the buried perovskite interface. This work demonstrates that a post-assembly nicotinic acid (NCA) interlayer effectively addresses these issues. The NCA treatment enhances the homogeneity and electrical conductivity of the underlying hole transport layer. Furthermore, the carboxylic acid groups in NCA forms hydrogen bonds with the formamidinium cations and coordinates to Pb2+ ions, mitigating perovskite lattice strain and passivating defects at the buried interface. Consequently, devices incorporating a post-assembly NCA layer achieve a champion PCE of 25.98% and demonstrated significantly enhanced operational stability under UV exposure compared to control devices. These findings establish post-assembly modification as a potent strategy to overcome inherent limitations in state-of-the-art SAM-based PSCs.