Rational design of isatin-based quinoidal conjugated polymers for efficient organic photovoltaics with dual donor ternary strategy

Abstract

The quinoid strategy is regarded as a promising approach for fabricating high-performance organic semiconductor materials. However, the applications of quinoidal conjugated polymers (QCPs) are mostly limited to organic field-effect transistors (OFETs), and their photovoltaic applications remain challenging. In this study, two novel QCPs, PQ-H and PQ-F, were designed and synthesized by incorporating isomer-free deep-energy-level quinoid units. Using them as third components, ternary organic photovoltaic (OPV) devices combining the polymer donor PM6 and small-molecule acceptor Y6 were fabricated in an inverted configuration. The complementary absorption behavior of the QCPs with PM6 and Y6 enhanced light harvesting. In particular, owing to the achievement of an ideal morphology by introducing QCPs, the fill factor (FF) and open-circuit voltage (VOC) of the ternary OPVs were improved. Consequently, by incorporating 1 wt% PQ-H and 2 wt% PQ-F in the ternary films, higher average power conversion efficiencies (PCE) of 14.16 % and 14.54 %, respectively, were recorded compared to that of PM6:Y6 binary OPVs (13.63 %). This study demonstrates that with a suitable molecular design approach, QCPs can act as photoactive materials and their small amounts can significantly affect the performance of ternary OPVs to enhance all photovoltaic parameters.