Benzodithiophene-Based Copolymers as Dopant-Free Hole-Transporting Materials for Perovskite Solar Cells

Over a decade, single-junction perovskite solar cells (PSCs) have achieved a remarkable power conversion efficiency of 26.4%. However, the pressing challenge remains to address their long-term stability for large-scale industrial production. A significant factor contributing to this instability is the use of doped hole-transporting materials (HTMs), which often introduce moisture into contact with the perovskite film, leading to its degradation. To address this issue, research has focused on developing novel and stable "dopant-free" HTMs. These materials possess inherent conductivity and can function without the need for additional dopants. These HTMs, constructed with donors and acceptors, have properties like film-forming abilities, tunable molecular weights, unique stacking, and high hole mobility. Among the classic donor units, benzodithiophene (BDT) has emerged as a widely utilized component for the synthesis of molecules and polymers for photovoltaic applications. To stimulate further research and optimization of these materials, this overview presents a comprehensive examination of various BDT-based dopant-free polymeric HTMs with different acceptor units within the field of PSCs. It provides a concise historical overview, followed by an in-depth classification and examination of polymeric structures. The exploration delves into their constituent building blocks, aiming to uncover the relationships between structure and activity wherever feasible. A concise and comprehensive overview on benzodithiophene (BDT)-based dopant-free polymeric hole-transporting materials (HTMs), incorporating various acceptor units like thienothiophene, benzodithiophene-dione, benzothiadiazole, benzotriazole, and thieno pyrrole-dione in perovskite solar cells, is described. This includes the classification and analysis of polymeric architectures, scrutinizing their constituent components to unveil structure-activity correlations in various BDT-based dopant-free polymeric HTMs.image (c) 2024 WILEY-VCH GmbH