General Considerations for Improving Photovoltage in Metal-Insulator-Semiconductor Photoanodes
I.A. Digdaya (TU Delft - ChemE/Materials for Energy Conversion and Storage)
Bartek J. Trzesniewski (TU Delft - ChemE/Materials for Energy Conversion and Storage)
Gede W.P. Adhyaksa (AMOLF Institute for Atomic and Molecular Physics)
E.C. Garnett (AMOLF Institute for Atomic and Molecular Physics)
Wilson A. Smith (TU Delft - ChemE/Materials for Energy Conversion and Storage)
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Abstract
Metal-insulator-semiconductor (MIS) photoelectrodes offer a simple alternative to the traditional semiconductor-liquid junction and the conventional p-n junction electrode. Highly efficient MIS photoanodes require interfacial surface passivating oxides and high workfunction metals to produce a high photovoltage. Herein, we investigate and analyze the effect of interfacial oxides and metal workfunctions on the barrier height and the photovoltage of a c-Si photoanode. We use two metal components in a bimetal contact configuration and observe the modulation of the effective barrier height and the resulting photovoltage as a function of the secondary outer metal. The photovoltage shows a strong linear dependence by increasing the inner metal workfunction, with the highest photovoltage achieved by a MIS photoanode using a platinum inner metal. We also found that coupling a thin aluminium oxide with an interfacial silicon oxide and controlling the oxide thickness can significantly improve the photovoltage of an MIS junction photoanode.
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