Efficient Organic Solar Cells with Polymer-Small Molecule: Fullerene Ternary Active Layers

[Image: see text] In this study, we report organic solar cells (OSCs) fabricated by a polymer-small molecule: the fullerene ternary active layer. It is found that a significantly enhanced power conversion efficiency contributed to the enhanced short-circuit current density and fill factor (FF). Investigation of absorption spectra and external quantum efficiency spectra indicate that the enhancement in photocurrent originates from the improved light absorption attributed to the small molecule. Further investigations by grazing-incidence wide-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy reveal that charge transport within the ternary active layer is facilitated by a reduced π–π distance between the adjacent polymer chains along the out-of-plane direction, good miscibilities between ternary components, and the rougher surface of the resultant thin film. As a result, the hole mobility of the polymer electron donor and electron mobility of the fullerene electron acceptor are considerably increased, resulting in enhanced FFs. Our studies provide a facile route to realize efficient OSCs.