An optically transparent cathode for dye sensitized solar cells based on cationically functionalized and metal decorated graphene

Optically transparent counter electrodes outperforming the conventional Pt counter electrodes in dye sensitized solar cells (DSSCs) are seldom reported. In this work, a highly transparent (similar to 88% at 550 nm) and catalytic (charge transfer resistance <1 Omega cm(2)) counter electrode based on a novel Pt polyelectrolyte functionalized graphene composite is demonstrated. Graphene sheets (HEG) are synthesized by hydrogen induced simultaneous exfoliation-reduction of graphite oxide. HEG is functionalized by a cationic polyelectrolyte, poly-diallyl-diammonium chloride (PDDA) which causes minimum damage to graphene and assists in uniform tethering of nanoparticles. Pt nanoparticles are decorated on PDDA-HEG by a simple microwave assisted polyol reduction method. Electrochemical impedance measurements and cylic voltammetry measurements show that the higher catalytic activity of Pt/PDDA-HEG is due to the presence of positive charges and nanostructured Pt. As a consequence, the DSSCs fabricated with Pt/PDDA-HEG counter electrode exhibits an enhanced power conversion efficiency of similar to 5.7% as compared to 4.5% for reference cells with Pt counter electrode. (C) 2012 Elsevier Ltd. All rights reserved.