Miscibility screening promotes the efficiency and stability of P3HT-based organic solar cells

The power conversion efficiency of organic photovoltaics (OPVs) has witnessed continuous breakthroughs in the past few years, mostly benefiting from the extensive use of a facile ternary blending strategy by blending the host polymer donor:small molecule acceptor mixture with a second small molecule acceptor. Nevertheless, this rather general strategy used in the well-known PM6 systems fails in constructing high-performance P3HT-based ternary OPVs. As a result, the efficiencies of all resulting ternary blends based on a benchmark host P3HT:ZY-4Cl and a second acceptor are no more than 8%. Employing the mutual miscibility of the binary blends as a guide to screen the second acceptor, here we were able to break the longstanding 10%-efficiency barrier of ternary OPVs based on P3HT and dual nonfullerene acceptors. With this rational approach, we identified a multifunctional small molecule acceptor BTP-2Br to simultaneously improve the photovoltaic performance in both P3HT and PM6-based ternary OPVs. Attractively, the P3HT:ZY-4Cl:BTP-2Br ternary blend exhibited a record-breaking efficiency of 11.41% for P3HT-based OPVs. This is the first-ever report that over 11% efficiency is achieved for P3HT-based ternary OPVs. Importantly, the study helps the community to rely less on trial-and-error methods for constructing ternary solar cells. With the rational guidance of miscibility screening, we designed and synthesized a versatile small molecule acceptor BTP-2Br to simultaneously improve the photovoltaic performance in both P3HT- and PM6-based ternary OPVs. The photovoltaic efficiency of the ternary blend based on P3HT:ZY-4Cl:BTP-2Br has reached 11.41%, which is a new world record for P3HT-based OPVs. image