Low-temperature titania-graphene quantum dots paste for flexible dye-sensitised solar cell applications

Graphene possesses excellent mechanical strength and chemical inertness with high intrinsic carrier mobility and superior flexibility making them exceptional candidates for optoelectronic applications. Graphene quantum dots (GQDs) derived from graphene domains have been widely explored to study their photoluminescence properties which can be tuned by size. GQDs are biocompatible, low cytotoxic, strongly luminescent and disperse well in polar and non-polar solvents showing bright promise for the integration into devices for bioimaging, light emitting and photovoltaic applications. In the present study, graphene quantum dots were synthesized by an electrochemical cyclic voltammetry technique using reduced graphene oxide (rGO). GQDs have been incorporated into binder free TiO ₂ paste and studied as a photoelectrode material fabricated on ITO/PEN substrates for flexible dye sensitised solar cells (DSSCs). DSSC based on GQDs-TiO ₂ exhibited open circuit output potential difference (V _oc ) of 0.73 V, and short circuit current density (J _sc ) of 11.54 mA cm ⁻² with an increment in power conversion efficiency by 5.48%, when compared with those with DSSC build with just a TiO ₂ photoanode (open-circuit output potential difference (V _oc ) of 0.68 V and short circuit density (J _sc ) of 10.67 mA cm ⁻² ). The results have been understood in terms of increased charge extraction and reduced recombination losses upon GQDs incorporation.