A study of SnO2/TiO2 core/shell films was undertaken to investigate the influence of shell thickness and post deposition sintering on electron localization and transport properties. Electrochemical reduction of the materials resulted in the appearance of a broad visible –near IR absorbance that provided insights into the electronic state(s) within the core/shell structures. As the shell thickness was increased from 0.5 nm to 5 nm, evidence for the presence of a SnχTi1-χO2 interfacial state emerged that was physically located between the core and the shell. The lifetime of photoinjected electrons increased with the shell thickness. Electron transport occurred through the SnO2 core, however when materials with shell thicknesses ≥2 nm were annealed at 450°C, a new electron transport pathway through the shell was evident. The data indicate that these materials are best described as SnO2/SnχTi1-χO2/TiO2 where electrons preferentially localize in a SnχTi1-χO2 interfacial state, and transport through SnO2 and annealed TiO2 (if present). The implications of these results for applications in solar energy conversion are discussed.
James, E.; Bennett, M. T.; Bangle, R. E.; Meyer, G. J. Electron Localization and Transport in SnO2/TiO2 Mesoporous Thin Films: Evidence for a SnO2/SnχTi1-χO2/TiO2 Structure. Langmuir 2019, 35 (39), 12694-12703. http://dx.doi.org/10.1021/acs.langmuir.9b02216