Molecular Conformation Governs Self-Assembled Monolayer Orientation for High-Performance Perovskite Photovoltaics.

Abstract

While highly ordered self-assembled monolayers (SAMs) are critically important for inverted perovskite solar cells (i-PSCs), precise control over molecular orientation remains a persistent challenge, hindering the concurrent achievement of high efficiency and long-term stability. To address this issue, we unveil that the molecular orientation of SAMs based on bis-carbazole phosphonates is governed by their conformational structures, which can be finely modulated through tailored carbazole-carbazole binding geometries. These structurally ordered layers provide a robust platform for deliberate energy level alignment and enhanced charge transport selectivity, enabling a certified power conversion efficiency of 27.2%, an impressive value that ranks among the highest reported for i-PSCs. Moreover, owing to the robust anchoring capability afforded by the bis-phosphonate design, the devices exhibit extended operational stability-retaining 96% of their initial efficiency after 1400 h under one-sun illumination and maximum power point tracking, and show excellent compatibility with scalable fabrication in ambient air. This work thus establishes a powerful chemical strategy for tailoring molecular orientation, providing a promising molecular design paradigm for advancing perovskite photovoltaics.