Performance improvement of polymer solar cells with binary additives induced morphology optimization and interface modification simultaneously

•DIO and PEG binary additives polymer solar cells was prepared.•DIO facilitate donor/acceptor phase separation.•PEG improves PTB7 crystallinity and enhance PEDOT:PSS conductivity.•Binary additives optimize active layer morphology and modify anode buffer layer simultaneously.•High short-circuit current density of 20.03 mA/cm2 achieved. Active layer morphology optimization and electrode buffer layer interface modification are commonly used strategies in improving the performance of polymer solar cells (PSCs). In this study, we prepared PTB7: PC71BM bulk heterojunction PSCs with 1,8-diiodooctane (DIO) and polyethylene glycol (PEG) additives, and studied the influence of binary additives on exciton dissociation, charge transport and charge extraction. DIO facilitates donor/acceptor phase separation for efficient exciton dissociation and charge transport. The migration of PEG from active layer to the PEDOT:PSS layer improves the crystallinity of PTB7, optimizes charge transport pathway, and enhances the conductivity of PEDOT:PSS layer. With the combined advantages of binary additives in active layer morphology optimization and anode buffer layer modification, the device exhibits a high short-circuit current density of 20.03 mA/cm2 and an improved power conversion efficiency. Binary additive provides a promising method to optimize active layer morphology and improve interfacial buffer layer of PSCs simultaneously.