Controlling electron transport rate and recombination process of TiO 2 dye-sensitized solar cells by design of double-layer films with different arrangement modes

A. M. Bakhshayesh, M. R. Mohammadi (Lead / Corresponding author), D. J. Fray

    Research output: Contribution to journalArticlepeer-review

    44 Citations (Scopus)

    Abstract

    TiO 2 dye-sensitized solar cells (DSSCs) in the form of double-layer films, containing an under-layer and an over-layer, with various crystal structures (i.e., anatase and rutile phases) and morphologies (i.e., nanoparticle and nanowire) were reported. It was found that the photovoltaic performance of TiO 2 DSSCs depends on the morphology, crystal structure, light scattering effect, optical band gap energy and arrangement of the under- and over-layer films. The double-layer solar cell made of anatase-TiO 2 nanoparticles as the under-layer and anatase-TiO 2 nanowires as the over-layer (i.e., AW solar cell) showed the highest power conversion efficiency and fill factor of 6.34% and 62.6%, respectively. High electron lifetime, rapid transportation and less recombination of photogenerated electrons are the factors affect the efficiency improvement of AW film and was demonstrated by electrochemical impedance spectroscopy (EIS). X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) analyses revealed that TiO 2 nanoparticles had uniform and nanometer grains with particle size around 20 nm, whereas TiO 2 nanowires with length of several μm had diameter in the range 20-50 nm. The optical properties and band gap energies of TiO 2 nanoparticles and nanowires were studied through UV-vis absorption. The indirect optical band gap energy of TiO 2 nanowires, anatase-TiO 2 and rutile-TiO 2 nanoparticles was calculated 3.61, 3.47 and 3.41 eV, respectively. The design of double-layer solar cells by manipulation of morphology and crystal structure of TiO 2 nanostructures will open a new concept for improvement of power conversion efficiency of dye sensitized solar cells.

    Original languageEnglish
    Pages (from-to)384-391
    Number of pages8
    JournalElectrochimica Acta
    Volume78
    Early online date30 Jun 2012
    DOIs
    Publication statusPublished - 1 Sep 2012

    Keywords

    • Double-layer
    • Dye-sensitized solar cell
    • EIS
    • TiO nanoparticles
    • TiO nanowires

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