The impressive effect of eco-friendly carbon dots on improving the performance of dye-sensitized solar cells

•A novel and green strategy used to synthesize carbon dots from Rosemary leaves.•CDs modified TiO2 in DSSC exhibit efficiencies up to 125% under one sun.•In the presence of CDs, recombination processes reduced dramatically.•In new designed DSSC, due to improved electron transport, Jcs increased. Herein, a novel and green strategy based on hydrothermal treatment was reported to synthesize highly water-soluble carbon dots from Rosemary leaves. A one-step, effective, low-cost and environmentally friendly method was used for the CDs preparation. Enhanced photoconversion efficiency of the TiO2-based dye-sensitized solar cell (DSSC), is observed in the presence of carbon dots. Though recombination processes are generally inappropriate for the power conversion of DSSC, the photoanode, which was constructed from CDs/TiO2 represented a significant increase in the power conversion efficiency compared to the pure TiO2. In the novel designed DSSC the power conversion efficiency was enhanced. This enhancement was occurred due to the improvement in the connection between the nanoparticles that leading to ameliorate the electron hopping at the nanoparticle’s boundaries and efficient charge carrier separations. A significant improvement in all cell parameters in the presence of CDs (5%)/TiO2 as a photoanode was observed. The improvement of Jsc. (=16.94 mA cm2) and Voc. (=0.788 mV) resulted a 2.2-fold increase in the power conversion efficiency compared to TiO2-based DSSC.