Selecting suitable material(s) for water splitting is an intricate dilemma because materials with high solar-to-hydrogen conversion efficiency are typically not stable in aqueous environment and/or are scarce, whereas stable and abundant materials exhibit unacceptably poor performance for commercialization. For example, Fe2O3 is an abundant n-type semiconductor that has excellent stability in neutral and alkaline electrolytes, but so far the reported solar-to-hydrogen conversion efficiency has not exceeded 3%. A major factor hampering the performance of water-splitting materials, such as Fe2O3, is the high charge recombination rate inside the semiconductor. Thus, there is a need to develop methods and designs to deterministically, and spatially, control, and in particular reduce, charge recombination. Here we show, by means of first-principles and experiment, that joining two different oxides can control the charge recombination rate. The control mechanism relies on the formation of dipole-like electric fields at the interface that, depending on the field direction, attract or repel minority carriers from the interface. We provide proof-of-principle demonstration of this approach by patterning the surface of Fe2O3, one of the most studied semiconductors for light-driven water splitting, with TiO2 and Cu2O nanodisks.

Tailoring charge recombination in photoelectrodes using oxide nanostructures

251st National Meeting (2016)

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