Carbazole-Based Self-Assembled Monolayers for Hole Transport in Photovoltaics: A Molecular Engineering Perspective

Abstract

Self-assembled monolayers (SAMs) have proven to be highly efficient hole-transporting layers (HTLs) due to their advantages, including low cost, minimal material consumption, ease of synthesis, negligible optical loss, and exceptional stability. Recently, carbazole-based SAM HTLs have considerably improved the power conversion efficiency (PCE) of organic solar cells (OSCs) and perovskite solar cells (PSCs)—with PCEs reaching 21% and 27%, respectively. This review begins with a concise overview of the chemical structure of SAMs, emphasizing the recent advancements achieved by carbazole-based SAMs in the photovoltaics (PVs) sector. We then systematically summarize the modifications made to the chemical structure of carbazole-based SAMs to optimize their interface dipole, surface wettability, and interface defects. Especially for functional group, the modification techniques are categorized into four main types: methoxylation, conjugation, halogenation, and asymmetrization. Finally, several challenges, including solubility, film quality, and stability, along with potential solutions for these issues are discussed. We hope this review serves as a valuable guide and source of inspiration for the design of SAM HTLs, ultimately enhancing the performance of PV devices.

Keywords

carbazole-derivative / chemistry structure modification / hole-transporting layers / self-assembled monolayers / solar cells

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