Development of bulk heterojunction morphology by the difference of intermolecular interaction behaviors

•We study the development of the bulk heterojunction morphologies of conjugated polymer/fullerene derivative blends in the presence of processing additives.•Solar cell performance is strongly dependent on the intermolecular interactions between the conjugated polymers in the photoactive layer.•Selection of the processing additive with the aim of enhancing photovoltaic performance needs to take into account the intermolecular interaction of the conjugated polymer.