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Identifying Charge Transfer Mechanisms across Semiconductor Heterostructures via Surface Dipole Modulation and
Ryan T Pekarek1, Kara Kearney2,3, Benjamin M Simon1
1Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States.
Journal of the American Chemical Society
|October 4, 2018
Summary
Hole transfer across TiO2-protected silicon photoanodes is controlled by interfacial molecular dipoles, occurring via thermionic emission or intraband tunneling. This study enhances understanding of charge transport in photoelectrochemical devices.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Science
Background:
- Efficient photoelectrochemical devices rely on complex heterojunctions.
- Understanding charge transport across these interfaces is crucial but challenging.
- Titanium dioxide (TiO2) is a common protective layer for semiconductors.
Purpose of the Study:
- To analyze hole transfer across n-Si(111)-R|TiO2 photoanodes.
- To investigate the role of interfacial molecular dipoles in charge transport.
- To develop and validate a multiscale computational model for predicting charge transport.
Main Methods:
- Experimental characterization: X-ray photoelectron spectroscopy, voltammetry, impedance spectroscopy.
- Computational modeling: First-principles density functional theory (DFT) and finite-element device modeling.
- Validation with nonaqueous redox couples (ferrocene derivatives).
Main Results:
- Hole transport is limited at the n-Si(111)-R|TiO2 interface.
- Charge transport occurs via thermionic emission and/or intraband tunneling, regulated by interfacial molecular dipoles.
- A combined DFT/device-modeling approach accurately predicted charge transport behavior.
Conclusions:
- Fundamental understanding of charge transport across TiO2-protected electrodes is provided.
- The predictive capability of the combined DFT/device-modeling approach is demonstrated.
- This work offers insights for designing stable and efficient photoelectrochemical devices.
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