Effect of Nanotube Morphologies on Multi-Walled Carbon Nanotubes Based Counter Electrode for Dye-Sensitized Solar Cell

Multi-walled carbon nanotubes (MWCNTs) with different morphologies were introduced into dyesensitized solar cell (DSSC) as low-cost substitutes for Pt counter electrode (CE). The effect of length and orientation of MWCNTs on the power conversion efficiency (PCE) of DSSC with MWCNTs CE were studied by measuring electrochemical impedance spectroscopy of MWCNTs and the photocurrent density–voltage (J–V ) characteristics of DSSC in this study. Results revealed that the long MWCNTs showed better electrocatalytic activity of reducing triiodide ions than short MWCNTs and yielded the power conversion efficiency of 2.42%. When the aligned multi-walled carbon nanotubes (AMWCNTs) with the same length as the long MWCNTs were used to prepare the CE, the power conversion efficiency of the DSSC reaches 2.95%. In order to further improve the performance of the DSSC, the processing of photoanode and counter electrode were adjusted. The power conversion efficiency of the cell with AMWCNTs as CE prepared by adjusted processing achieved 3.95% and the short circuit current density is superior to the DSSC with Pt as CEs, and it indicated the adjusted processing is beneficial to increase the overall performance of the dye-sensitized solar cell.