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.