PEG-functionalized graphene quantum dots for efficient organic solar cells

Abstract

Organic photovoltaic (OPV) solar cells are promising candidates for future power generation needs due to their low-cost, ease of processing, and flexibility. In efforts to improve efficiency, graphene quantum dots (GQDs) have been studied as a supplemental material in the active layer, but the fundamental role of GQDs and their functional groups remains unknown. In this work, we have shown a significant improvement in OPV effi-ciency (nearly 40%) using GQDs functionalized with various molecular weights of PEG. Through use of UV-Vis analysis on P3HT/PCBM thin films, we found that the active layer absorption increase of GQD-containing de-vices originates from faster P3HT exciton dissociation, an explanation confirmed with faster decay constants extracted from TA-spectroscopy. Functionalization with PEG was shown to further boost this mechanism by promoting charge transfer, resulting in the shortest molecular weight (200 MW) producing the highest cell efficiency.