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Browsing by Author "Parreira, P."

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  • Coumarin dye with ethynyl group as p-spacer unit for dye sensitized solar cells
    Publication . Torres, Erica; Sequeira, S.; Parreira, P.; Mendes, Paulo; Silva, Tiago J. L.; Lobato, Killian; Brites, Maria João
    C1-LEN coumarin dye, containing an ethynyl conjugated bridge was tested as a new chromophore for dye-sensitized solar cells (DSSCs). Investigation on the relationship of dye structure, optical properties, electrochemical properties and performance of DSSCs is described. The C1-LEN-sensitized solar cells showed an overall conversion efficiency of 2.2% (JSC = 6.11 mA/cm2, VOC = 547 mV, FF = 0.66), which corresponds to 68% of N719-based device efficiency, fabricated under similar conditions. Electrochemical impedance spectroscopy (EIS) analysis reveals that charge recombination at the nanocrystalline TiO2/dye/redox electrolyte interface is similar for C1-LEN and N719 sensitized solar cells, i.e., charge recombination is not the factor limiting the performance of C1-LEN device.
    2015Journal article Open access Show more
  • Dye-sensitized 1D anatase TiO2 nanorods for tunable efficient photodetection in the visible range
    Publication . Parreira, P.; Torres, Erica; Nunes, Clarisse; Carvalho, C. Nunes de; Lavareda, G.; Amaral, A.; Brites, Maria João
    TiO2 films with enhanced photosensitivity were deposited on alkali free glass substrates without intentional substrate heating by pulsed DC magnetron reactive sputtering with an average thickness of about 2 μm. Three dyes, commercial N719 and two new organic dyes were impregnated in order to control the optical spectral selectivity of such films. The type of dye used proved to dramatically influence the device's response to radiation pulses. The practical breakthrough is the use of different dyes according to the region of the electromagnetic spectrum one wants to detect. Devices with photocurrent 6 orders of magnitude higher than the dark current (from ∼2 × 10−12 to 2 × 10−6 A for a 100 V bias) were fabricated with a spectral response within the visible range of the electromagnetic spectrum. In addition, this approach is likely to allow for the fabrication of hybrid photodetectors on cheap heat sensible flexible polymeric substrates.
    2012Journal article Open access Show more