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 Title: ELEMENT-SPECIFIC MEASUREMENT OF HOLE TRANSPORT IN A Ni-TiO2-Si PHOTOLECTRODE USING TRANSIENT EXTREME ULTRAVIOLET SPECTROSCOPY Author(s): Cushing, Scott Kevin Subject(s): Mini-symposium: High-Harmonic Generation and XUV Spectroscopy Abstract: A passivating oxide layer is critical for the stability and the performance of solar-fuel photoelectrodes. While the semiconductor surface can be passivated by a few nanometer oxide film, the best performance often correlates with a thicker and defect-rich amorphous TiO$_{2}$ layer. The defect states are suggested to facilitate hole transport between the semiconductor and metal catalyst. In this presentation, transient extreme ultraviolet (XUV) absorption spectroscopy quantifies the electron and hole transport between each element of a photoexcited Ni-TiO$_{2}$-Si photoelectrode. A ballistic hole tunneling from the p-type Si to the Ni metal is measured in 100 fs after photoexcitation of the Si. The measured hole injection efficiency is 26\%. The transient hole population is then measured to back-diffuse through the TiO$_{2}$ on a picoseconds timescale, followed by an increased electron-hole recombination at the Si-TiO$_{2}$ interface. By temporally resolving the population of electrons and holes in each layer of the junction, the hole transport velocity in the TiO$_{2}$, the hole mobility in the Si, the diffusion constant of holes in the TiO$_{2}$, and the surface recombination velocity at the Si/TiO$_{2}$ interface are quantized. Issue Date: 2019-06-18 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/104225 DOI: 10.15278/isms.2019.TK07 Rights Information: Copyright 2019 Scott Kevin Cushing Date Available in IDEALS: 2019-07-152020-01-25
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