Effect of ultra-thin ZnO coating layer on the device performance of TiO2 dye sensitized solar cell

Abstract

The device performance of a dye sensitized solar cell (DSSC) is sensitive to the electronic band structure and the surface chemical states of the TiO2 photo electrode. In this study, the electronic band structure alignment in a DSSC was modified by coating a nano-meter thick ZnO layer on TiO2 by RF magnetron sputtering. The electron recombination at the interface of ZnO/TiO2 and dye/electrolyte was suppressed, resulting in an increased open-circuit voltage and fill factor. The short-circuit current decreased exponentially with increased ZnO thickness. The transport of the injected electron in the ZnO to the TiO2 conduction band occurred by tunneling when the ZnO thickness is less than 2.2nm.