Understanding the Effect of the Third Component PC₇₁BM on Nanoscale Morphology and Photovoltaic Properties of Ternary Organic Solar Cells

Herein, PC₇₁BM is used as the third component (the second acceptor) to improve the photovoltaic performance of the organic solar cells (OSCs) based on a low-cost polymer donor PTQ10 and a nonfullerene small-molecule acceptor Y6. The ternary OSCs based on PTQ10:Y6:PC₇₁BM reach a higher power conversion efficiency (PCE) of 16.07% with enhanced short-circuit current density and a better fill factor in comparison with the binary OSCs based on PTQ10:Y6, which is ascribed to the higher electron mobility, better charge extraction, and suppressed charge recombination of the ternary PSCs. The film morphology of the OSCs is studied by grazing-incidence wide-angle X-ray scattering, photo-induced force microscopy, and transmission electron microscopy, which reveals that with the treatment of additive (0.5% CN) and thermal annealing, the phase separation of Y6 is obviously enhanced, whereas no significant changes occur for that of PTQ10 component. Besides, the addition of PC₇₁BM slightly lowers the ratio of the face-on orientation in the blend film and attenuate the aggregation of acceptor Y6. In addition, compared with the binary PTQ10:Y6 OSC, the ternary device based on PTQ10:Y6:PC₇₁BM shows better device stability, demonstrating a great potential for the practical application of ternary OSCs.