Molecular design of A Non-Fullerene Acceptor Enables P3HT-Based Organic Solar Cell with 9.46% Efficiency

The advantage in low cost makes P3HT one of the most attractive electron donors for photovoltaic applications, but the power conversion efficiency (PCE) of the P3HT-based organic solar cells (OSCs) remains low (7-8%). Herein, to modulate phase separation morphology so as to enhance the PCE in P3HT-based OSC, a new NFA, namely ZY-4Cl, is designed and synthesized by modifying the cyano-substituted end groups in BTP-4Cl. The P3HT:ZY-4Cl based OSC exhibits a significantly improved PCE of ~9.5%, which is a new record for the P3HT-based OSCs. Furthermore, two model compounds, TT-CN and TT-O, are synthesized to simulate the end groups of BTP-4Cl and ZY-4Cl, respectively. The calculated Flory-Huggins interaction parameter, the DSC and AFM results clearly indicate that the cyano-substituted compound TT-CN shows much stronger miscibility with P3HT compared to TT-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 a NFA with a high PCE for P3HT-based OSC, but also suggests a guidance for the molecular design of NFAs from the aspect of morphology control.