Graphene quantum dot derivatives as anode/cathode interlayers for polymer solar cells

Abstract

The interlayers play critical roles in polymer solar cells (PSCs), and the development of novel interfacial materials is an efficient way to improve the device performance. We have developed graphene quantum dot (GQD) based interfacial materials, which is different from the conventional interfacial materials, such as semiconducting polymers, inorganic metal oxide, low work-function metals or salts, and polyelectrolytes. Compared with graphene oxide (GO), the edge-carboxylated graphene quantum dots (EC-GQDs) contain single oxygen species of carboxyl groups (COOH). EC-GQD based interfacial materials can improve the device performance of PSCs owing to their controllable chemical modification and tunable opto-electronic properties. EC-GQD itself can be used as anode interlayer to gain excellent device performance due to the high work-function and good film-forming property. Through chemical functionalization of EC-GQD from the COOH, the alkali metal cations, quaternary ammonium salts and other polar groups can be incorporated at the edge. The functionalized GQD can significantly decrease the work-function of electrodes, and thus can be used as the cathode interlayers for PSCs. In this review, we systemically introduced the unique structure of EC-GQDs, their chemical modification and the application of GQD-based interfacial materials in PSCs.