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Updated: Jun 3, 2026

Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers
Published on: September 27, 2018
A two-dimensional phase of TiO₂ with a reduced bandgap
Junguang Tao1, Tim Luttrell, Matthias Batzill
1Department of Physics, University of South Florida, Tampa, Florida 33620, USA.
Abstract:
Titanium dioxide is the prototypical transition metal oxide photocatalyst. However, the larger than 3 eV bandgap of common bulk phases of TiO₂ limits its light absorption to UV light, making it inefficient for solar energy conversion. Attempts at increasing visible light activity by narrowing the bandgap of TiO₂ through doping have proven difficult, because of defect-induced charge trapping and recombination sites of photo-excited charge carriers. Here, we report the existence of a dopant-free, pure TiO₂ phase with a narrow bandgap. This new pure TiO₂ phase forms on the surface of rutile TiO₂(011) by oxidation of bulk titanium interstitials. We measure a bandgap of only ~2.1 eV for this new phase, matching it closely with the energy of visible light.
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