Post-plasma treatment of a carbon nanowall for use as a counter electrode in a dye-sensitized solar cell

Abstract

This research investigates plasma-treated carbon nanowalls (CNW) for use as counter electrodes in dye-sensitized solar cells (DSSCs). The CNWs were synthesized on a fluorine-tin-oxide (FTO) glass substrate via microwave plasma-enhanced chemical vapor-deposition (PECVD) using CH₄ gas. Then, post-plasma treatments were performed on the CNWs in different plasma environments (using O₂, H₂ and N₂ gas) under the same conditions, after which DSSCs were fabricated using the plasma-treated CNWs as counter electrodes. Scanning electron microscopy (SEM) was performed to obtain cross-sectional and planar images of the CNWs, and Raman spectroscopy was used to analyze the structural characteristics of the post-plasma-treated synthesized CNWs. The energy conversion efficiency was then used to analyze the effect of using the plasma-treated CNWs as counter electrodes in the DSSCs. The DSSC for which the as-deposited CNW was used as a counter electrode showed an energy conversion efficiency of 1.64%, and the DSSC with the H₂ postplasma-treated CNW counter electrode showed an energy conversion efficiency of 2.23%. Thus, the DSSC with the H₂-treated electrode presented a 36% higher efficiency than the DSSC with the as-deposited CNW electrode.