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Abstract:
Titania (TiO2) is frequently used in photovoltaic
and photocatalytic applications, despite the fact that its
main optical absorption occurs only at ∼4 eV. Absorption
across the band gap of 3 eV is dipole-forbidden in rutile TiO2.
By means of first-principles theoretical spectroscopy calculations,
we demonstrate that alloying with TiS2 introduces an
absorption band into the fundamental gap of TiO2. In
addition, band-edge transitions contribute to optical absorption
because the S incorporation breaks the symmetry of the
TiO2 lattice. Both effects lead to pronounced absorption of visible light for S concentrations as low as 1.5%.