1. Wasted photons: photogeneration yield and charge carrier collection efficiency of hematite photoanodes for photoelectrochemical water splitting
- Author
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David S. Ellis, Avner Rothschild, Yifat Piekner, Daniel A. Grave, and Anton Tsyganok
- Subjects
Photocurrent ,Range (particle radiation) ,Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,Band gap ,02 engineering and technology ,Hematite ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Pollution ,0104 chemical sciences ,Nuclear Energy and Engineering ,visual_art ,Yield (chemistry) ,visual_art.visual_art_medium ,Environmental Chemistry ,Optoelectronics ,Water splitting ,Charge carrier ,0210 nano-technology ,business ,Absorption (electromagnetic radiation) - 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.
- Published
- 2021