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Issue 6, 2019
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Stable and tunable phosphonic acid dipole layer for band edge engineering of photoelectrochemical and photovoltaic heterojunction devices

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Abstract

A key challenge for photoelectrochemical water splitting is that high performance semiconductors are not stable in aqueous electrolytes, necessitating corrosion protection layers such as TiO2. In the best case, the protection layer would also serve as the heterojunction partner, minimizing complexity and thereby cost. However, the bands of most high performance semiconductors are poorly aligned with TiO2, limiting the photovoltage. Here, we describe a method to overcome this limitation through the placement of a tunable dipole layer at the interface of the p- and n-type materials, shifting the relative band positions to enable an increased photovoltage. The introduction of a phosphonic acid (PA, H3PO3) layer increases the photovoltage of TiO2-protected Si, Sb2Se3, and Cu2O photocathodes. The dipole effect scales with PA surface coverage, and gives even larger shifts when multilayers are employed. By varying the thickness from submonolayer to multilayer (up to 2 nm), we are able to tune the photovoltage of p-Si/TiO2 over a range of 400 mV.

Graphical abstract: Stable and tunable phosphonic acid dipole layer for band edge engineering of photoelectrochemical and photovoltaic heterojunction devices

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Supplementary files

Article information


Submitted
05 Mar 2019
Accepted
26 Apr 2019
First published
26 Apr 2019

This article is Open Access

Energy Environ. Sci., 2019,12, 1901-1909
Article type
Paper

Stable and tunable phosphonic acid dipole layer for band edge engineering of photoelectrochemical and photovoltaic heterojunction devices

R. Wick-Joliat, T. Musso, R. R. Prabhakar, J. Löckinger, S. Siol, W. Cui, L. Sévery, T. Moehl, J. Suh, J. Hutter, M. Iannuzzi and S. D. Tilley, Energy Environ. Sci., 2019, 12, 1901
DOI: 10.1039/C9EE00748B

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