Optimizing the Multiwall Carbon Nanotubes Counter Electrode by Depositing CuS Quantum Dots

For the purpose of improving the property of a multiwall carbon nanotubes (MWCNTs) counter electrode (CE), CuS quantum dots (QDs) are deposited. Three-dimension network MWCNTs as the framework are deposited onto an fluorine-doped tin oxide (FTO) glass substrate and then CuS QDs as active sites are loaded onto them with a successive ionic layer adsorption and reaction method to form a composite CE. TEM and energy dispersive X-ray (EDX) spectrum can verify the morphology and elemental composition of the composite CE that CuS QDs are loaded onto the MWCNTs CE successfully. The photoelectric properties of quantum dot sensitized solar cells (QDSCs) are analyzed with Nyquist, Tafel, and J-V curves. The results show that the catalytic ability of the CE is enhanced through the loading of CuS QDs according to electrochemical impedance spectroscopy and Tafel analyses. The effect of CuS depositing cycle times on the photoelectric properties of QDSCs is discussed. And the QDSC based on the MWCNTs CE deposited with CuS QDs in ten cycles can display the best performance within all cell samples (V
_oc
= 0.874 V, J
_sc
= 10.105 mA cm
^-2
, FF = 0.416, and η = 3.677%). The power conversion efficiency of this cell is almost equivalent to that of Pt CE one under the same conditions and especially its V
_oc
is 0.118 V higher than that of the Pt CE.