Regioregular Non-Fused Polymerized Small Molecular Acceptors Enabling Efficient All-Polymer Solar Cells

The regioregularity induced by the isomers of the end-groups has been widely recognized as a key factor that determines the photovoltaic properties of polymerized small molecular acceptors (PSMAs) in all-polymer solar cells (all-PSCs). However, the influence of regioregularity on the photovoltaic properties of non-fused PSMAs has not been explored yet. In this contribution, two regioregular non-fused PSMAs, PFBTz-T-gamma and PFBTz-T-delta, were synthesized for the first time by using the monomers with isomeric pure end-groups. Compared with PFBTz-T-delta, PFBTz-T-gamma has more compact and more ordered packing in solid state, which results in a more red-shifted optical absorption and a higher electron mobility. More remarkably, PFBTz-T-gamma and PFBTz-T-delta exhibited huge difference in photovoltaic performance in all-PSCs, which offered the power conversion efficiencies (PCEs) of 9.72% and 0.52%, respectively. Further studies have unveiled that the higher PCE of PFBTz-T-gamma is due to more efficient exciton dissociation, higher and more balanced electron/hole mobility, and less charge recombination as a result of favorable morphology of the blend film. This work demonstrates that the development of regioregular non-fused PSMAs by tuning the polymerization sites is an effective strategy for obtaining high-efficiency all-PSCs.