Oxidation and Photooxidation of Single Crystal BiI3(001) Surfaces in Aqueous or Oxygen Environments
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open in viewerBiI3 is a non-toxic solar absorber material that is well matched for tandem-junction photovoltaic devices. We synthesized single-crystal samples via chemical vapor transport and physical vapor transport in evacuated ampoules to yield BiI3 flakes with mm2-to-cm2 terraces and explored the effect of various oxidizing atmospheres. Oxidation methods included immersion in degassed water, ultraviolet illumination under an oxygen ambient, and a sequence of ultraviolet illumination under oxygen and subsequent water immersion. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) quantified the chemical changes as a function of oxidative treatments. Spectra reveal that water immersion of BiI3 yields BiOI(102) reflections that are thicker than photoelectron probe depths. Ultraviolet illumination under an oxygen ambient forms bismuth oxide that subsequently converts to BiOI(001) upon water immersion. We discuss the implications of these surface chemical transformations for the long-term atmospheric stability of BiI3-containing solar energy conversion devices.
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- etd-64726
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- 2022
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- 2022-04-27
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