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

Comprehensive Summary 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‐ γ and PFBTz‐T‐ δ , were synthesized for the first time by using the monomers with isomeric pure end‐groups. Compared with PFBTz‐T‐ δ , PFBTz‐T‐ γ 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‐ γ and PFBTz‐T‐ δ 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‐ γ 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.