Recent progress in molecularly tailored organic hole transporting materials for highly efficient perovskite solar cells

Abstract

Over the last decade, perovskite solar cells (PSCs) have made remarkable progress, with power conversion efficiencies (PCEs) of single junction devices now surpassing >26%. A key component of this advancement is the use of hole transporting materials (HTMs), which are essential for efficient transport and collection of holes from the perovskite layer to the anode electrode. Spiro-OMeTAD and PTAA have been the leading HTMs; however, they face significant challenges including limitations on further performance enhancement, significant production costs and reliance on hygroscopic dopants that can compromise the long-term stability of PSC devices. This review discusses alternative pathways to HTMs, focusing on organic conjugated frameworks suitable for commercial use. It highlights recent innovations in organic HTMs, such as π-extended organic small molecules and polymeric candidates, as well as organic self-assembled monolayers (SAMs), which enhance both the efficiency and stability of Pb and Sn-based-PSCs. Additionally, this review reports successful design and synthetic strategies employed to discover high-performance PSCs and considers future advancements that could improve the commercial viability of PSCs. Furthermore, potential role of organic-HTMs in suppressing the formation of metallic lead (Pb⁰) on the perovskite surface is explained. By addressing the challenges associated with current HTMs and exploring innovative materials and design approaches, this review aims to contribute to the ongoing development of PSC technology, ultimately facilitating a broader adoption of this promising renewable energy solution.