Artículos SCI

Here we analyze the effect of two relevant aspects related to cell preparation on quantum dot sensitized solar cells (QDSCs) performance: the architecture of the TiO ₂ nanostructured electrode and the growth method of quantum dots (QD). Particular attention is given to the effect on the photovoltage, V _oc, since this parameter conveys the main current limitation of QDSCs. We have analyzed electrodes directly sensitized with CdSe QDs grown by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). We have carried out a systematic study comprising structural, optical, photophysical and photoelectrochemical characterization in order to correlate the material properties of the photoanodes with the functional performance of the manufactured QDSCs. The results show that the correspondence between photovoltaic conversion efficiency and the surface area of TiO ₂ depends on the QDs deposition method. Higher V _oc values are systematically obtained for TiO ₂ morphologies with decreasing surface area and for cells using CBD growth method. This is systematically correlated to a higher recombination resistance of CBD sensitized electrodes. Electron injection kinetics from QDs into TiO ₂ also depends on both the TiO ₂ structure and the QDs deposition method, being systematically faster for CBD. Only for electrodes prepared with small TiO ₂ nanoparticles SILAR method presents better performance than CBD, indicating that the small pore size disturb the CBD growth method. These results have important implications for the optimization of QDSCs.Elect

CdSe@ZnS nanocrystals have been prepared by a two-step solid state mechanochemical synthesis. CdSe prepared from elements in the first step is mixed with ZnS synthesized from zinc acetate and sodium sulfide in the second step. The crystallite size of the new type CdSe@ZnS nanocrystals determined by X-ray diffraction Rietveld refined method was 35 nra and 10 Jam for CdSe and ZnS, respectively. Energy dispersive/transmission electron microscopy/energy dispersive spectroscopy methods show good crystallinity of the nanoparticles and scanning electron microscopy elemental mapping illustrate consistent distribution of Cd, Se, Zn and S elements in the bulk of samples. UV-VIS spectra show an onset at 320 urn with calculated bandgap 3.85 eV. This absorption arises from the vibration modes of Zn-S bonds. The nanocrystals show the blue shift from the bandgap of bulk ZnS (3.66 eV). The synthesized CdSe@ZnS nanocrystals have been tested for dissolution, cytotoxicity and L-cysteine conjugation. The dissolution of Cd was less than 0.05 mu g mL(-1) (in comparison with 0.8 mu g mL(-1) which was evidenced for CdSe alone). The very low cytotoxic activity for selected cancer cell lines has been evidenced. CdSe@ZnS nanocrystals coated with L-cysteine are water-soluble and have a great potential in biomedical engineering as fluorescent labels.