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1

FeS2 quantum dots sensitized nanostructured TiO2 solar cell: photoelectrochemical and photoinduced absorption spectroscopy studies

Bedja I.

Materials Science Poland

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2011

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Vol. 29, No. 3

171--176

EN

Thin films of nanostructured TiO2 have been modified with FeS2 (pyrite) nano-particles by a low temperature chemical reaction of iron pentacarbonyl with sulfur in xylene. Quantum size effects are manifested by the observation of a blue shift in both absorption and photocurrent action spectra. PIA (Photoinduced absorption spectroscopy), where the excitation is provided by a square-wave modulated (on/off) monochromatic light emitting diode, is a multipurpose tool in the study of dye-sensitized solar cells. Here, PIA is used to study quantum-dot modified TiO2 nanostructured electrodes. The PIA spectra obtained give evidence for long-lived photoinduced charge separation: electrons are injected into the metal oxide and holes are left behind in the FeS2 quantum dot. Time-resolved PIA shows that recombination between electrons and holes occurs on a millisecond timescale. The Incident-Photon-to-Current Efficiency of about 23 % was obtained at 400 nm excitation. The performances of TiO2 electrodes modified with FeS2 are relatively low, which is explained by the presence of FeS2 phases other than the photoactive pyrite phase, as follows from the XRD spectrum.

2

Photoelectrochemical characterization of nitrogen-modified TiO2

Janczarek M., Kisch H., Hupka J.

Physicochemical Problems of Mineral Processing

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2007

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Vol. 41

158-166

EN

Modification of the chemical structure of titanium dioxide by non-metal elements (nitrogen) allows to move photocatalytic activity of titanium dioxide towards visible light. Three samples of photocatalysts with different nitrogen content and different photocatalytic properties were prepared for photoelectrochemical characterization. The positions of valence and conduction band edges of obtained semiconductors were calculated which enabled better understanding of the mechanism of visible light activity of the photocatalysts.

PL

Modyfikacja chemicznej struktury tlenku tytanu(IV) poprzez pierwiastki niemetaliczne (np. azot) jest jednym ze sposobów przesunięcia aktywności fotokatalitycznej tlenku tytanu(IV) w kierunku światła widzialnego. Trzy próbki katalizatorów o różnej zawartości azotu i różnych właściwościach fotokatalitycznych zostały wybrane do charakterystyki fotoelektrochemicznej, której efektem finalnym jest określenie położenia pasma wzbronionego i pasma przewodzenia w otrzymanych półprzewodnikach, co ma istotne znaczenie dla lepszego zrozumienia mechanizmu aktywności przygotowanych fotokatalizatorów w świetle widzialnym.

3

Photoresponse of Undoped and W-Doped TiO2

Radecka M., Sobaś P., Trenczek A., Rękas M.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 10

1925-1934

EN

Undoped andW-doped polycrystalline TiO2 were investigated. The kinetics of recombination processes has been studied. The flat band potential of TiO2 was determined (-0.11 V in respect to saturated calomel electrode, at pH = 7.8). Basing on the photocurrent experiments, the effect of Wconcentration on solar energy conversion efficiency was discussed. It was found, that addition ofWleads to an increase of solar-to-hydrogen energy efficiency. The maximum energy conversion efficiency has been observed for voltage bias ca 0.65 V. The highest energy conversion efficiency has been observed for TiO2 doped with 0.1 at % W.