Well defined double layers via binary solvent mixtures for highly efficient inverted all-polymer solar cells

Abstract

All-polymer solar cells have consistently attracted much attention to the planar heterojunction structures. However, key issues limiting the efficiency of bilayer all-polymer solar cells (BAPSCs) are their poor charge carrier transport and the strong possibility of recombination because of poorly organized double layer structures. Here we suggest well defined active systems via solvent engineering techniques for highly efficient BAPSCs. Thus, we systematically processed the single/co-solvents in each or both planar heterofilms, and investigated their morphological effects and device performances by charge carrier kinetics. Notably, more ordered molecular packing with stronger face-on stacking resulted from the co-solvent-treated active films, as revealed by atomic force microscopy and detailed two-dimensional grazing incidence wide-angle X-ray scattering measurements. Furthermore, these well-crystallized double layers enabled more efficient charge carrier movement, resulting in higher device efficiency. Our novel process offers an effective and facile method for precise control of the active layer morphology and a route to more efficient BAPSCs.