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A Novel Concept for Photovoltaic Cells: Clusters of Titanium Dioxide Encapsulated within Zeolites as Photoactive Semiconductors

Authors

  • Mercedes Álvaro Dr.,

    1. Instituto de Tecnología Química CSIC-UPV and Departamento de Química UPV Avda. de los Naranjos s/n, 46022 Valencia, Spain, Fax: (+34) 963-87-78-09
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  • Esther Carbonell,

    1. Instituto de Tecnología Química CSIC-UPV and Departamento de Química UPV Avda. de los Naranjos s/n, 46022 Valencia, Spain, Fax: (+34) 963-87-78-09
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  • Pedro Atienzar,

    1. Instituto de Tecnología Química CSIC-UPV and Departamento de Química UPV Avda. de los Naranjos s/n, 46022 Valencia, Spain, Fax: (+34) 963-87-78-09
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  • Hermenegildo García Prof. Dr.

    1. Instituto de Tecnología Química CSIC-UPV and Departamento de Química UPV Avda. de los Naranjos s/n, 46022 Valencia, Spain, Fax: (+34) 963-87-78-09
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Abstract

Discrete clusters of TiO2 (of only a few titanium atoms) are prepared within the internal micropore space of zeolite Y (4.8 wt % Ti loading) and characterized by Raman spectroscopy (rutile- and anatase-like structures), electron microscopy combined with elemental analyses (coincident Si and Ti spatial distribution), and X-ray diffraction (minor zeolite crystallinity decrease). The parent TiO2@Y sample is modified either by adsorption of acid-organic compounds (benzoic and 4-aminobenzoic acids or catechol) or by nitrogen doping. After modification, the optical UV/Vis spectrum of the parent TiO2@Y (onset of the absorption band at wavelengths <300 nm and bandgap of 4.2 eV) changes, and the appearance of new bands expanding to the visible region is observed. In contrast to the inactive zeolite Y matrix, all the zeolite-encapsulated TiO2 species exhibit a photovoltaic response. The influence of the I2/I3 concentration in the electrolyte solution on the temporal profile of the photovoltage clearly shows that I2/I3 is also a suitable carrier for the positive charge in zeolite-based photovoltaic devices. The photocurrent response and the efficiency of the photovoltaic cell based on zeolite-encapsulated TiO2 materials depend on the nature of the organic modifier and on the N-doping. The most efficient photovoltaic cell is that based on N-doped TiO2@Y, which exhibits a VOC (voltage at open circuit) of 270 mV, an ISC of 5.8 μA (current at short circuit), and a fill factor (FF) of 0.4. Although these values are low compared to current dye-sensitized TiO2 solar cells, our findings could open up a promise for a stimulating research on the photovoltaic activity of zeolite-based host–guest solids.

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