Honeycomb-like polypyrrole/multi-wall carbon nanotube films as an effective counter electrode in bifacial dye-sensitized solar cells

Honeycomb-like polypyrrole/multi-wall carbon nanotube (PPy/MWCNT) film demonstrates as an efficient and semitransparent counter electrode (CE) in bifacial dye-sensitized solar cell (DSSC), which is first fabricated on fluorine-doped tin oxide glass by a facile method using a sacrificial template of poly(methyl methacrylate) (PMMA). The results from ultraviolet-visible spectrophotometer and cyclic voltammetry measurements testify that the honeycomb-like PPy/MWCNT film possesses high transparency for the backside illumination and wonderful electrocatalytic activity for the reduction of triiodide (I-3 (-)) to iodide (I-) in the bifacial DSSC. Electrochemical impedance spectroscopy results indicate that the honeycomb-like nanostructure combining with the MWCNT decreases the resistance of the PPy/MWCNT film for the transfer of electrons from the external circuit back to the redox electrolyte. The bifacial DSSC based on the honeycomb-like PPy/MWCNT CE achieves 7.07 and 4.11% of the front and rear efficiencies, respectively, which are higher than those of the bifacial DSSC based on the flat PPy CE (5.78 and 3.07%, respectively).