Morphological Characterization of PffBT4T-2OD-Based Ternary Organic Solar Cells*

Ternary organic solar cells (TOSCs), consisting of one/two or two/one donor/acceptor, are a promising strategy for broadening the light absorption spectrum and enhancing the power conversion efficiency (PCE) of photovoltaic devices. In this study, the ternary blend system made use of PffBT4T-2OD (C₆₂H₈₈F₂N₂S₅)_n organic semiconductor as a donor (D) and PC70BM, N2200, and IDIC (C₆₆H₆₆N₄O₂S₂) acceptors (A) and their photovoltaic properties were studied through optimizing processing parameters such as polymer concentration, D:A1:A2 ratio and annealing. The effect of these parameters on the structural, morphological, electrical and photovoltaic properties were systematically investigated by performing UV-Vis absorption, Grazing-Incidence Wide-Angle X-ray Scattering (GiWAXS) and energy-filtered transmission electron microscopy (EFTEM). This work shows a PffBT4T-2OD-based ternary system composed of morphologically compatible acceptors can achieve a remarkable PCE >8%, significant enhancement of short-circuit current and the fill factor. We attribute that the high morphology compatibility of the ternary system can benefit to optimize electron/hole mobility and diminish recombination.