Graphene Quantum Dots/CdS/CdSe Co-Sensitized Solar Cells

Using three-dimensional anatase TiO2 microspheres as light scattering overlayer and commercial TiO2 nanocrystalline as connecting underlayer, novel double-layered TiO2 films were prepared by a doctor blade method for quantum dots sensitized solar cell (QDSSC) application. The graphene quantum dots (GQDs) were introduced by dripping, and the CdS/CdSe quantum dots were deposited by continuous ion-layer adsorption (SILAR) method, respectively. The prepared quantum dots sensitized thin films were characterized by field emission scanning electron microscopy, transmission electron miscroscopy, X-ray diffraction, Uv-vis diffuse reflectance spectra, and fluorescence spectra. CdS/CdSe quantum dots sensitized and GQDs/CdS/CdSe co-sensitized solar cells were fabricated, respectively. And the effects of GQDs and CdS quantum dots with different deposition cycles on the microstructures and the photovoltaic performance of the double-layered TiO2 QDSSCs were investigated and discussed. The results revealed that the introduced GQDs and the CdS deposition cycle obviously influenced the optical properties of the double-layered TiO2 film. The electron transfer and charge-recombination process are also affected by the CdS deposition cycle and the introduced GQDs. Optimally, the conversion efficiency and photocurrent density of the TiO2/QGDs/CdS(4)/CdSe solar cell is 1.24% and 9.47 mA/cm(2), respectively, which are higher than those (0.59% and 6.22 mA/cm(2), respectively) of the TiO2/CdS(4)/CdSe cell. This is due to the effective electrons transport and reduced charge recombination within the co-sensitized cell.