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

## TL;DR

This review explores how self-assembled monolayers improve the efficiency and stability of perovskite solar cells, while identifying key challenges and future research directions.

## Contribution

The paper provides a comprehensive analysis of the structure–property relationships and mechanisms of SAMs in inverted perovskite solar cells, along with a strategic roadmap for future development.

## Key findings

- SAMs enhance IPSC performance through energy-level alignment and defect passivation.
- SAMs improve carrier transport and suppress ion migration, leading to higher efficiency and stability.
- Large-scalable fabrication methods for SAMs are summarized to support industrial applications.

## Abstract

Structure–property relationship of self-assembled monolayers (SAMs) is thoroughly elucidated, including chain length, anchoring groups, linker groups, terminal functional groups, and packing density—and their resulting physical and electrochemical properties (e.g., wettability, adhesion, and electronic characteristics).The mechanism of SAMs on promoting the performance of inverted perovskite solar cells is discussed from the perspective of energy-level alignment, defect passivation, carrier transfer dynamics, and inhibition of ion migration.Perspectives and challenges of SAMs are proposed, highlighting promising directions in developing new in situ characterizations, advanced molecular designs, and optimized deposition strategies for large-scalable fabrication.

Structure–property relationship of self-assembled monolayers (SAMs) is thoroughly elucidated, including chain length, anchoring groups, linker groups, terminal functional groups, and packing density—and their resulting physical and electrochemical properties (e.g., wettability, adhesion, and electronic characteristics).

The mechanism of SAMs on promoting the performance of inverted perovskite solar cells is discussed from the perspective of energy-level alignment, defect passivation, carrier transfer dynamics, and inhibition of ion migration.

Perspectives and challenges of SAMs are proposed, highlighting promising directions in developing new in situ characterizations, advanced molecular designs, and optimized deposition strategies for large-scalable fabrication.

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.