Self-Assembled Monolayers in Inverted Perovskite Solar Cells: A Rising Star with Challenges

Recently, self-assembled monolayers (SAMs) have been confirmed as a promising hole-selective contact and interfacial modifier for inverted perovskite solar cells (IPSCs), contributing to an inspiring record power conversion efficiency close to 27%, along with excellent stability. This review demonstrates the critical role of SAMs in enhancing the performance of IPSCs. First, the structure-property and structure-stability relationship of SAMs is systematically expounded by examining their electronic structure, spatial configuration, and the resulting intermolecular forces. Second, it concludes the underlying mechanisms how their unique properties promote the performance of IPSCs, including energy-level alignment, defect passivation, improved interface carrier extraction/transport, and the suppression of ion migration. Third, the applications of SAMs in IPSCs are systematically summarized, covering their roles as hole-selective contacts, interface modifiers, and as components in Co-SAMs strategies. Large-scalable fabrication methods are also summarized to promote industrial processing of IPSCs. Finally, the prevailing challenges and future research directions are outlined, proposing a roadmap for designing SAM-based IPSCs with superior longevity. By critically evaluating the pivotal role of SAMs, this review provides a strategic framework to guide future research and accelerate the development of self-assembled molecules in high-performance and stable photovoltaic devices.