Our goal is to develop a more ideal protection layer using transition metal oxide-titania alloys synthesized by ALD. An ideal protection layer should be corrosion resistant, highly conductive, and enable a high photovoltage. For n-type silicon Schottky photoanodes, this means that the protection layer must also possess a high work function. We previously demonstrated that TiO2-RuO2 alloys composed of 13-46% Ru were highly conductive and consistently achieved photovoltages >525 mV without any post-processing anneals.6 The built-in field was set by the TiO2-RuO2 alloy, which possessed a sufficiently high work function of 5.02 eV. Although TiO2-RuO2 alloys were ideal Schottky contacts to nSi, they lacked the long-term corrosion resistance required of a protection layer. RuO2 is known to be unstable at the conditions required for water oxidation. We also report on ALD alloys of TiO2 and IrO2, which exhibit high conductivity and photovoltage > 600 mV on nSi, but with improved stability. Additionally, TiO2-IrO2 alloys are capable of catalyzing oxygen evolution. Thus, TiO2-IrO2alloys have the potential to be an “all-in-one” catalyst, Schottky contact, and corrosion resistant protection layer.
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