期刊
PHYSICAL REVIEW LETTERS
卷 112, 期 3, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.112.036404
关键词
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资金
- U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division
- National Science Foundation [DMR-1151687]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1151687] Funding Source: National Science Foundation
Recent studies indicated that noncompensated cation-anion codoping of wide-band-gap oxide semiconductors such as anatase TiO2 significantly reduces the optical band gap and thus strongly enhances the absorption of visible light [W. Zhu et al., Phys. Rev. Lett. 103, 226401 (2009)]. We used soft x-ray spectroscopy to fully determine the location and nature of the impurity levels responsible for the extraordinarily large (similar to 1 eV) band gap reduction of noncompensated codoped rutile TiO2. It is shown that Cr/N codoping strongly enhances the substitutional N content, compared to single element doping. The band gap reduction is due to the formation of Cr 3d(3) levels in the lower half of the gap while the conduction band minimum is comprised of localized Cr 3d and delocalized N 2p states. Band gap reduction and carrier delocalization are critical elements for efficient light-to-current conversion in oxide semiconductors. These findings thus raise the prospect of using codoped oxide semiconductors with specifically engineered electronic properties in a variety of photovoltaic and photocatalytic applications.
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