Photovoltaic improvement and charge recombination reduction by aluminum oxide impregnated MWCNTs/TiO2 based photoanode for dye-sensitized solar cells

The photovoltaic performance of dye-sensitized solar cells was investigated by incorporation of Al2O3 impregnated multi-walled carbon nanotubes (MWCNTs) and without impregnated MWCNTs in TiO2. The composites of Al2O3-MWCNTs and MWCNTs with TiO2 were prepared by a direct mixing technique. The dispersions of Al2O3-MWCNTs and MWCNTs in TiO2 were confirmed by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) analysis confirms the interstitial incorporation of carbon atoms in the TiO2 lattice via O–Ti–C and Ti–O–C surface states. The solar cells assembled by using composite photoanodes were characterized by UV-Visible absorption spectroscopy measurement, photocurrent–voltage characteristics, and electrochemical impedance spectroscopy. The results showed that upon optimization the device made of Al2O3-0.10%CNTs/TiO2, 0.10%CNTs/TiO2 and pristine TiO2 showed an overall conversion efficiency of 7.02, 5.94 and 5.02 respectively. The improvement in the efficiency of Al2O3-MWCNTs/TiO2 based DSSC can be attributed to an enhanced short-circuit current and reduction in charge recombination. We also employed density functional theory (DFT) to find the band gaps of Al2O3-CNTs/TiO2, CNTs/TiO2 and pristine TiO2.