Electron transport in dye sensitized solar cells with TiO2/ZnO core-shell photoelectrode

This paper presents the electron transport in dye sensitized solar cell (DSSC) with TiO₂/ZnO core-shell photoelectrode. Sol-gel processed ZnO was used to form the shell layer on TiO₂ nanoparticles. DSSC with TiO₂/ZnO core-shell photoelectrode resulted in 32 % enhancement in the overall photoconversion efficiency compared to DSSC with conventional TiO₂ photoelectrode. Dark, illuminated current-voltage characteristics (I-V) and external quantum efficiency (EQE) of the DSSC with TiO₂/ZnO core-shell photoelectrode suggest that formation of ZnO shell on TiO₂ nanoparticles can effectively prevent the electron back reaction from the conduction band of the mesoporous TiO₂ to the surface states and eventually suppressed the recombination of the photoexcited electrons with either a hole available in electrolyte or oxidized dye molecules. The enhancement in short circuit density (J_SC) and open circuit voltage (V_OC) confirmed the suppressed density and activity of surface states at TiO₂/ZnO/dye/electrolyte interfaces compared to TiO₂/dye/electrolyte interfaces.