Improve the efficiency of organic solar cells by creating a favorable charge transport channel with a halogen-free additive

In optimizing the mixed film morphology of organic solar cells (OSCs), conventional additives such as 1,8-diiodooctane (DIO) has an important role to play. Anyway, the toxicity inhibits their further development. Here, a new non-toxic, halogen-free additive called Methyl Benzoate (MBZ) has been added into the classic OSCs (PTB7-Th: PC71BM). A series of characterizations demonstrate that the MBZ additive effectively matches well with the active layer material and enhances the formation of network interpenetrating structures. This enhances charge transport and inhibits the recombination of excitons. Power conversion efficiency (PCE) of 8.76% and fill factor (FF) of 70.9% are achieved by the device with the MBZ additive. This research paves the way for future large-scale industrial deployment about organic solar cells (OSCs) by presenting a method for replacing conventional additives with halogen-free alternatives.