Tunable Nonthermal Distribution of Hot Electrons in a Semiconductor Injected from a Plasmonic Gold Nanostructure
Abstract
For semiconductors photosensitized with organic dyes or quantum dots, transferred electrons are usually considered thermalized at the conduction band edge. This study suggests that the electrons injected from a plasmonic metal into a thin semiconductor shell can be nonthermal with energy up to the plasmon frequency. In other words, the electrons injected into the semiconductor are still hot carriers. Photomodulated X-ray absorption measurements of the Ti L_(2,3) edge are compared before and after excitation of the plasmon in Au@TiO_2 core–shell nanoparticles. Comparison with theoretical predictions of the X-ray absorption, which include the heating and state-filling effects from injected hot carriers, suggests that the electrons transferred from the plasmon remain nonthermal in the ∼10 nm TiO_2 shell, due in part to a slow trapping in defect states. By repeating the measurements for spherical, rod-like, and star-like metal nanoparticles, the magnitude of the nonthermal distribution, peak energy, and number of injected hot electrons are confirmed to be tuned by the plasmon frequency and the sharp corners of the plasmonic nanostructure. The results suggest that plasmonic photosensitizers can not only extend the sunlight absorption spectral range of semiconductor-based devices but could also result in increased open circuit voltages and elevated thermodynamic driving forces for solar fuel generation in photoelectrochemical cells.
Additional Information
© 2018 American Chemical Society. Received: April 19, 2018; Accepted: June 26, 2018; Published: June 26, 2018. J. Li prepared the three samples used in this work including gold nanopshere@TiO_2, nanorod@TiO_2 and nanostar@TiO2 when he was employed at West Virginia University. P. Zheng helped with TEM characterization. C. J. Chen and R. S. Liu thank the support from the Ministry of Science and Technology of Taiwan (contract no. MOST 104-2113-M-002-012-MY3). The authors declare no competing financial interest.Attached Files
Supplemental Material - nn8b02939_si_001.pdf
Files
Name | Size | Download all |
---|---|---|
md5:fcba30633cfce534fb33fa6f19894317
|
672.3 kB | Preview Download |
Additional details
- Eprint ID
- 89702
- Resolver ID
- CaltechAUTHORS:20180918-130828386
- Ministry of Science and Technology (Taiwan)
- MOST 104-2113-M-002-012-MY3
- Created
-
2018-09-18Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field