2D/1A Strategy to Regulate Film Morphology for Efficient and Stable Nonfullerene Organic Solar Cells

Recently, the ternary blend method has been successfully applied to nonfullerene organic solar cells (OSCs) and enhanced the device performance by utilizing complementary optical absorption. Here we demonstrate the two polymer donors and one small-molecule acceptor (i.e., 2D/1A) strategy to finely regulate the blend film morphology in fullerene-free OSCs. One crystalline polymer donor, PffBT4T–2OD, can act as an effective morphology regulator for a benchmark blend of PTB7–Th and ITIC, leading to appropriate phase-separated morphology, suppressed charge recombination, efficient charge transport and high carrier mobility. The resulting solvent additive- and annealing-free fabricated bulk-heterojunction OSCs show the best power conversion efficiency (PCE) of 8.22% with a significant increase of fill factor compared to their binary counterparts. Importantly, such ternary OSCs when processed under ambient condition retain excellent device performance with a PCE of 7.57%, indicative of good air-stability.