Manipulating molecular aggregation and crystalline behavior of A‐DA'D‐A type acceptors by side chain engineering in organic solar cells

Alkyl chains engineering plays an important role in photovoltaic materials for organic solar cells. Herein, three A-DA'D-A (acceptor–donor–acceptor'–donor–acceptor) type acceptors named Y6, Y6-C4, and Y6-C5 with different branching position on the pyrrole motif are discussed relationship between molecular aggregation, crystalline, device performance systematically investigated. The distance main backbone affects their optical absorption energy levels. Y6-C4 at fourth fifth carbon of alkyl chain show blue-shifted increased electrochemical bandgaps, compared Y6 second side chain. In addition, this influences aggregation crystalline behavior donor/acceptor blends. Compared possesses a stronger aggregate ability blends lower non-radiative loss, which results higher open circuit voltage (Voc) 0.88 V. Finally, Y6-C5-based binary achieved high power conversion efficiency up to 16.73% afill factor (FF) 0.78. These demonstrate that is effective strategy tuning improve acceptors.