Noncovalent functionalization of graphene attaching [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and application as electron extraction layer of polymer solar cells.

A new graphene-fullerene composite (rGO-pyrene-PCBM), in which [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was attached onto reduced graphene oxide (rGO) via the noncovalent functionalization approach, was reported. The pyrene-PCBM moiety was synthesized via a facile esterification reaction, and pyrene was used as an anchoring bridge to link rGO and PCBM components. FTIR, UV-vis, and XPS spectroscopic characterizations were carried out to confirm the hybrid structure of rGO-pyrene-PCBM, and the composite formation is found to improve greatly the dispersity of rGO in DMF. The geometric configuration of rGO-pyrene-PCBM was studied by Raman, SEM, and AFM analyses, suggesting that the C60 moiety is far from the graphene sheet and is bridged with the graphene sheet via the pyrene anchor. Finally rGO-pyrene-PCBM was successfully applied as electron extraction layer for P3HT:PCBM bulk heterojunction polymer solar cell (BHJ-PSC) devices, affording a PCE of 3.89%, which is enhanced by ca. 15% compared to that of the reference device without electron extraction layer (3.39%). Contrarily, the comparative devices incorporating the rGO or pyrene-PCBM component as electron extraction layer showed dramatically decreased PCE, indicating the importance of composite formation between rGO and pyrene-PCBM components for its electron extraction property.