PBDB-T and its derivatives: A family of polymer donors enables over 17% efficiency in organic photovoltaics

Due to the advantages such as being low cost, light weight, and flexible as well as having low toxicity, organic solar cells (OSCs) have attracted extensive interest. The field of OSCs progressed dramatically after the emergence of non-fullerene small molecule acceptors. In addition to the development of these acceptor materials, a key driver in the rapid progress of OSC research was the introduction of the PBDB-T polymer and its derivatives. In this review, we first give a brief overview of the structural features of PBDB-T congeners and the strategies used to design these polymers. The interesting aggregation effects of PBDB-T congeners in solution and solid-states are highlighted. Recent advances in the morphological understanding OSCs based on PBDB-T congeners are discussed using selected examples. In addition, the versatile applications of PBDB-T congeners in OSC devices, including interfacially modified binary, ternary and tandem devices, are also summarized. Importantly, we assess the energy loss and provide a meta-analysis of a library of high-performance PBDB-T type polymers, which are compared with other types of conjugated polymers. Finally, the remaining questions and the prospects of these exciting polymers are suggested.