Charge Transfer from PbS Quantum Dots to Insulating TiO 2 Matrix
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R. KONENKAMP AND P. HOYER Hahn-Meitner Institut Berlin, Glienicker Str. 100, 14109 Berlin, Germany
ABSTRACT We report on the photoconductivity of thin films consisting of a porous nanocrystalline TiO2 matrix and quantum size PbS clusters adsorbed on the inner surfaces of the TiO2. The PbS clusters are typically a few nm in size and are not connected. Due to quantum confinement the bandgap of the clusters is widened to around 2 eV from the 0.41 eV value for PbS bulk. The clusters thus absorb in the visible spectrum. However, due to their spatial separation, photoconductance through the film requires carrier transfer through the TiO2 matrix. Our data show this to occur only for clusters
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