Recent advances on aromatic-diimide based cathode interfacial materials for polymer solar cells

As an emerging photovoltaic technology, polymer solar cells (PSCs) have attracted broad interest for both academic and industry communities due to their outstanding advantages, such as lightweight, low cost and easy to process in large areas. In recent years, the power conversion efficiency of PSCs has been improved rapidly, exceeding 17% for the state-of-the-art devices. For device optimization, it has been demonstrated that the efficiency and stability can be significantly improved by constructing efficient organic cathode interfacial materials. Specially, aromatic-diimide based cathode interfacial materials have attracted much attention due to their advantages of excellent electron transport, easily chemical modification and suitable energy levels. In this review, along with the briefly introduction on the basic functions of cathode interlayer, recent progress of cathode interlayer based on perylene diimides and naphthalene diimides was summarized. At last, the perspective and challenge were proposed according to the requirements of practical application.