Visible light carrier generation in co-doped epitaxial titanate films

Journal Article · Mon Mar 02 00:00:00 EST 2015 · Applied Physics Letters, 109(9):Article No. 092901

DOI:https://doi.org/10.1063/1.4913930· OSTI ID:1184281

Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason; Chambers, Scott A.

Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity—which may be valuable in photovoltaic applications—and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance measurements confirm that optically generated carriers have a recombination lifetime comparable to that of STO and are in agreement with the observations from ellipsometry. Finally, through photoelectrochemical yield measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830; BES DMSE 10122
• OSTI ID: 1184281
• Alternate ID(s): OSTI ID: 1226716
• Report Number(s): PNNL-SA-107663; 48341
• Journal Information: Applied Physics Letters, 109(9):Article No. 092901, Journal Name: Applied Physics Letters, 109(9):Article No. 092901
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory