Issue 8, 2021

Wasted photons: photogeneration yield and charge carrier collection efficiency of hematite photoanodes for photoelectrochemical water splitting

Abstract

Hematite (α-Fe2O3) is a leading photoanode candidate for photoelectrochemical water splitting. Despite extensive research efforts, the champion hematite photoanodes reported to date have achieved less than half of the maximal photocurrent predicted by its bandgap energy. Here we show that this underachievement arises, to a large extent, because of unproductive optical excitations that give rise to localized electronic transitions that do not generate electron–hole pairs. A comprehensive method for extraction of the photogeneration yield spectrum, the wavelength-dependent fraction of absorbed photons that generate electron–hole pairs, and the spatial charge carrier collection efficiency is presented, and applied for a thin (32 nm) film hematite photoanode. Its photogeneration yield is less than unity across the entire absorption range, limiting the maximal photocurrent that may be attained in an ideal hematite photoanode to about half of the theoretical limit predicted without accounting for this effect.

Graphical abstract: Wasted photons: photogeneration yield and charge carrier collection efficiency of hematite photoanodes for photoelectrochemical water splitting

Supplementary files

Article information

Article type
Paper
Submitted
10 Jun 2021
Accepted
15 Jul 2021
First published
15 Jul 2021

Energy Environ. Sci., 2021,14, 4584-4598

Wasted photons: photogeneration yield and charge carrier collection efficiency of hematite photoanodes for photoelectrochemical water splitting

Y. Piekner, D. S. Ellis, D. A. Grave, A. Tsyganok and A. Rothschild, Energy Environ. Sci., 2021, 14, 4584 DOI: 10.1039/D1EE01772A

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