Graphene loaded TiO2 submicron spheres scattering layer for efficient dye-sensitized solar cell

Enhancement effect of biomass-derived carbon quantum dots (CQDs) on the performance of dye-sensitized solar cells (DSSCs)

Corn stover, an agricultural waste, was used to prepare nitrogen self-doped carbon quantum dots (CQDs) through a simple hydrothermal method with only water at near room temperature for the first time. The surface, electrochemical, and photovoltaic characteristics of CQDs doped TiO2 in dye-sensitized solar cells (DSSCs) were thoroughly and systematically examined. The average diameter of blue-fluorescence CQDs measured by a high-resolution transmission electron microscope (HR-TEM) was 4.63 ± 0.87 nm, which consisted of polar functional groups. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy of the biomass-derived CQDs, determined by the cyclic voltammetry (CV) test, were, -5.48 eV and -3.89 eV, respectively. The negative shift of flat band potential (Vfb) in CQDs incorporated photoanode implies the fermi level shifted upward. Experimental results revealed that the improved performance of DSSCs was due to charge transport enhancement and separation, which resulted in the improved energy level configuration between TiO2, CQDs, and electrolytes. In this regard, the CQDs serve as a mediator that enables charge carrier transport without hindrance. In this study, CQDs added to TiO2 + N719, increased short circuit current density (JSC) and power conversion efficiency (PCE) value by ∼26.00 % (10.13 to 12.69 mA/cm2) and 27.20 % (4.78 % to 6.08 %), respectively.

Graphene oxide doping in tropical almond (terminalia catappa L.) fruits extract mediated green synthesis of TiO2 nanoparticles for improved DSSC power conversion efficiency

The power conversion efficiency (PCE) of a dye-sensitized solar cell (DSSC) device depends on its semiconductor characteristics. Titanium dioxide (TiO2) nanoparticles are a semiconductor material commonly used in the DSSC device whose characteristics depend on the synthesis process. There are many routes to synthesize TiO2, however, they typically involve hazardous approaches, which may cause risk to the environment. Green synthesis is an environmentally friendly alternative method using ecological solvents that eliminates toxic waste and reduces energy consumption. In this work, tropical almond (Terminalia catappa L.) was used as a natural capping agent in the green synthesis to control the growth of TiO2. In addition, graphene oxide (GO) was used as a dopant to increase the performance of DSSC device. The results are convincing, in which the addition of 0.0017 % GO doping in tropical almond extract mediated green synthesis of TiO2 improved the PCE from 0.85 % to 1.72 %. These results suggest that GO-modified TiO2 nanoparticles green synthesized using tropical almond extract have great potential in the fabrication of DSSC devices with good PCE, low cost, and low environmental impact.