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A Novel Concept for Photovoltaic Cells: Clusters of Titanium Dioxide Encapsulated within Zeolites as Photoactive Semiconductors
Author(s) -
Álvaro Mercedes,
Carbonell Esther,
Atienzar Pedro,
García Hermenegildo
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600162
Subject(s) - materials science , photocurrent , titanium dioxide , band gap , anatase , solar cell , photoactive layer , open circuit voltage , rutile , raman spectroscopy , zeolite , chemical engineering , analytical chemistry (journal) , inorganic chemistry , photocatalysis , chemistry , polymer solar cell , optoelectronics , organic chemistry , optics , engineering , metallurgy , catalysis , physics , voltage , quantum mechanics
Discrete clusters of TiO 2 (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 TiO 2 @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 TiO 2 @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 TiO 2 species exhibit a photovoltaic response. The influence of the I 2 /I 3 − concentration in the electrolyte solution on the temporal profile of the photovoltage clearly shows that I 2 /I 3 − 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 TiO 2 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 TiO 2 @Y, which exhibits a V OC (voltage at open circuit) of 270 mV, an I SC 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 TiO 2 solar cells, our findings could open up a promise for a stimulating research on the photovoltaic activity of zeolite‐based host–guest solids.