Optimization of TiO2/MWCNT composites for efficient dye sensitized solar cells

This paper deals with the effects of introducing multiwall carbon nanotubes (MWCNTs) into photoanodes of dye sensitized solar cells (DSSCs). Mesoporous titanium dioxide (TiO2) nanoparticles were synthesized using sol–gel technique. TiO2/MWCNT composites were prepared by adding functionalized MWCNTs to TiO2 nanoparticles using two different surfactants (α-terpineol and Triton X-100). Nanoparticles and composites were characterized using Dynamic Light Scattering spectrophotometer, Raman spectrometer, X-ray diffractometer, field emission scanning electron microscope, Brunauer–Emmett–Teller surface area analyzer and UV–Vis spectrophotometer. FESEM depicted that particles were spherical in shape and their size decreased due to addition of MWCNTs. This was attributed to the decrease in the crystallite size which in turn confirmed by XRD. UV–Vis absorption spectra showed the better absorbance for the visible range of light, as the content of MWCNT is increased. From the Tauc plot optical band gap was calculated and noted that it declined gradually with the content of MWCNTs. BET surface area increased drastically which was attributed to the formation of more number of pores in the nanocomposites as visualized from FESEM. UV–Vis spectra of dye desorbed from the photoanode revealed that the dye adsorption increased as a function of MWCNT wt%. I–V studies were carried out under the illumination of 100 mW/cm2 simulated sunlight. Photoanodes prepared by both the methods showed better performance compared to pristine TiO2 photoanode, because of high conducting path and high surface area provided by MWCNTs. Photoanodes with 0.19 wt% MWCNTs in them were able to achieve maximum efficiency of 3.54 and 3.86% for method A and B respectively