Enhanced Optical Absorption Due to Symmetry Breaking in TiO_2(1–x)S_2x Alloys

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%.     «

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 bre...     »