Graphitic carbon nitride/multiwalled carbon nanotubes composite as Pt-free counter electrode for high-efficiency dye-sensitized solar cells

A graphitic carbon nitride (g-C 3 N 4 )/multiwalled carbon nanotubes (MWCNT) composite is prepared by a combination of refluxing process and heating polymerization and investigated as the counter electrode in dye-sensitized solar cells. SEM and TEM studies indicate that MWCNT is very well incorporated and attached to g-C 3 N 4 . Electrochemical impedance spectroscopy demonstrates that the charge-transfer resistance of g-C 3 N 4 /MWCNT composite electrode is 2.1 Ω cm 2 , which is much lower than those of the individual g-C 3 N 4 and MWCNT electrodes. This enhanced electrocatalytic activity is beneficial for improving the photovoltaic performance of dye-sensitized solar cells. Under illumination of 100   mW   cm −2 , the dye-sensitized solar cell based on g-C 3 N 4 /MWCNT counter electrode achieves a conversion efficiency of 6.34%, which is comparable to that of the cell based on Pt counter electrode.