Process optimization of dye-sensitized solar cells using $$\hbox {TiO}₂$$ TiO 2 –graphene nanocomposites

(hbox {TiO}₂)–graphene (TGR) nanocomposites with varying concentrations of graphene from 0 to 1 wt% were prepared by direct mix method. X-ray diffraction (XRD) spectra confirmed the incorporation of graphene in photoanode material, which was further supported by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX). The UV–visible spectrum of these nanocomposites shifted towards higher wavelength region as compared to pure (hbox {TiO}₂) that indicated a reduced band gap and hence, enhanced absorption bandwidth. Significant reduction in electron–hole recombination was confirmed from photoluminescence spectroscopy. These TGR nanocomposite films after tethering with black dye were employed as photoanodes in dye-sensitized solar cells (DSSCs). The efficiency of solar cells at varying concentrations of graphene (in photoandes) was also investigated. TGR 0.25 wt% nanocomposite showed the highest photocurrent density ((J_{mathrm{SC}})) of (18.4,hbox {mA},hbox {cm}^-2) and efficiency ((eta )) of 4.69%.