Molecular design of a non-fullerene acceptor enables aP3HT-based organic solar cell with 9.46% efficiency

The advantage of low cost makesP3HTone of the most attractive electron donors for photovoltaic applications, but the power conversion efficiency (PCE) of theP3HT-based organic solar cells (OSCs) remains low (7-8%). Herein, to modulate the phase separation morphology so as to enhance the PCE inP3HT-based OSCs, a new NFA, namelyZY-4Cl, is designed and synthesized by modifying the cyano-substituted end groups inBTP-4Cl. TheP3HT:ZY-4Clbased OSC exhibits a significantly improved PCE of similar to 9.5%, which is a new record for theP3HT-based OSCs. Furthermore, two model compounds,TT-CNandTT-O, are synthesized to simulate the end groups ofBTP-4ClandZY-4Cl, respectively. The calculated Flory-Huggins interaction parameter, the DSC and the AFM results clearly indicate that the cyano-substituted compoundTT-CNshows much stronger miscibility withP3HTcompared toTT-O, the one without cyano groups. This molecular design strategy is also verified in the other two representative NFAs. Therefore, this work not only reports an NFA with a high PCE forP3HT-based OSCs, but also suggests guidance for the molecular design of NFAs from the aspect of morphology control.