Molecular-scale interface engineering of metal nanoparticles for plasmon-enhanced dye sensitized solar cellsElectronic supplementary information (ESI) available. See DOI: 10.1039/c3dt32741h

A molecular surface chemical treatment is introduced into a dye sensitized solar cell (DSSC) incorporating metal nanoparticles to suppress the charge recombination. Dodecanethiol molecules as a surface treatment agent are successfully anchored onto the exposed Au nanoparticle sites of the ZnO nanorods/Au nanoparticles/N719 photoanode. ATR-FTIR and Raman measurements are conducted to understand the adsorptions of different molecules (dodecanethiol, N719) on the ZnO nanorods and Au nanoparticles surface. The effects of the dodecanethiol surface treatment on the performance of the plasmon-enhanced DSSC are investigated by UV-vis absorption, incident photon-to-current conversion efficiency (IPCE) and electrochemical impedance spectroscopy (EIS). The plasmon-enhanced light absorption due to the presence of Au nanoparticles is not affected by the dodecanethiol surface treatment. The charge recombination on the ZnO nanorods-dye-electrolyte interface is substantially retarded by insulating the exposed Au nanoparticle sites from the oxidized form of the electrolyte via dodecanethiol molecules. The strategy of a molecular surface chemical treatment on the photoanode of a DSSC with metal nanoparticles fully exploits the plasmon-enhanced light absorption and explores a simple method to protect the metal nanoparticles for the plasmon-enhanced DSSC. In plasmon-enhanced dye-sensitized solar cells, charge recombination is retarded by the surface treatment with dodecanethiol molecules.