Doped graphene electrodes for organic solar cells

Abstract

In this work graphene sheets grown by chemical vapor deposition (CVD) with controllednumbers of layers were used as transparent electrodes in organic photovoltaic (OPV)devices. It was found that for devices with pristine graphene electrodes, the powerconversion efficiency (PCE) is comparable to their counterparts with indium tin oxide(ITO) electrodes. Nevertheless, the chances for failure in OPVs with pristinegraphene electrodes are higher than for those with ITO electrodes, due to thesurface wetting challenge between the hole-transporting layer and the grapheneelectrodes. Various alternative routes were investigated and it was found thatAuCl3 doping on graphene can alter the graphene surface wetting properties such that auniform coating of the hole-transporting layer can be achieved and device successrate can be increased. Furthermore, the doping both improves the conductivityand shifts the work function of the graphene electrode, resulting in improvedoverall PCE performance of the OPV devices. This work brings us one step furthertoward the future use of graphene transparent electrodes as a replacement for ITO.