Issue 5, 2015

Extracting large photovoltages from a-SiC photocathodes with an amorphous TiO2 front surface field layer for solar hydrogen evolution

Abstract

A thin film heterojunction photocathode is fabricated by depositing an n-type amorphous titanium dioxide (TiO2) onto a p-type/intrinsic hydrogenated amorphous silicon carbide (a-SiC). Using this configuration, the photovoltage of the photocathode increases from 0.5 V to 0.8 V under open circuit conditions, indicating the change in band-edge energetics from the semiconductor–liquid junction to the isolated solid p–i–n junction. The p–i–n structure produces an internal electric field that increases the operating photovoltage, and subsequently improves the drift mechanism of photogenerated charge carriers across the intrinsic layer. The enhancement of the photovoltage leads to a very positive photocurrent onset potential of +0.8 V vs. RHE and exhibits a photocurrent density of 8.3 mA cm−2 at 0 V vs. RHE with only a 100 nm absorber layer. The a-SiC photocathode with a front surface field amorphous TiO2 layer shows a high stability for 12 hours of operation under photocatalytic conditions. This high performance, very thin, and earth-abundant photocathode is very promising for integration with smaller band gap solar absorbers to form a multijunction system for highly efficient bias-free solar water splitting devices.

Graphical abstract: Extracting large photovoltages from a-SiC photocathodes with an amorphous TiO2 front surface field layer for solar hydrogen evolution

Supplementary files

Article information

Article type
Paper
Submitted
09 Mar 2015
Accepted
02 Apr 2015
First published
08 Apr 2015

Energy Environ. Sci., 2015,8, 1585-1593

Author version available

Extracting large photovoltages from a-SiC photocathodes with an amorphous TiO2 front surface field layer for solar hydrogen evolution

I. A. Digdaya, L. Han, T. W. F. Buijs, M. Zeman, B. Dam, A. H. M. Smets and W. A. Smith, Energy Environ. Sci., 2015, 8, 1585 DOI: 10.1039/C5EE00769K

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