Morphology control through incorporation of an asymmetric small molecule donor for efficient ternary organic solar cells

Abstract

Morphology control of the active layer is the key to achieving a high power conversion efficiency (PCE) for organic solar cells (OSCs). The strategy of incorporating small molecule donors as the third component to construct ternary OSCs has emerged as an effective approach to regulate morphology. In this regard, we employed an asymmetric strategy to synthesize the small molecule donor SBDT-Asy. In the asymmetric core, the rigid benzene ring was employed as one side chain, which was expected to disrupt the self-aggregation and stir the PM6:Y6 host blend. For the other side chain, we introduced alkoxyl chains to improve solubility. As a result, the ideal film morphology could be achieved. Benefiting from enhanced exciton dissociation and charge transport resulting from the good morphology, the PCE of PM6:Y6:SBDT-Asy ternary devices increased to 17.68%. The results presented in this work suggest that introducing small molecules containing an asymmetric core is an effective approach to develop high-efficiency ternary OSCs.