Accelerated ageing of molybdenum oxide

Marina Jorge, Simon Cooil, Mark T. Edmonds, Lars Thomsen, Mohammadreza Nematollahi, Federico Mazzola, Justin W. Wells

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    Abstract

    The stability and lifetime of materials proposed for photovoltaic applications are important parameters, because such devices should offer long-term reliable performance whilst operating in a harsh environment. In this work, we present a powerful approach to accelerate and study the degradation mechanisms of molybdenum oxide, a material which has shown promise for next generation photovoltaics, and for enhanced hole extraction in organic photovoltaics. We use UV and soft x-rays to drive accelerated ageing, boosting the ageing time by a factor of up to 1000. Using this method, we find that molybdenum oxide does not offer reliable performance in environments in which heating or ionising radiation are present, because of its propensity to reduce, thus strongly modifying its electronic properties. We estimate that  ≈100 d of unfiltered sunlight exposure would be sufficient to reduce this material into metallic MoO2. We also show that a very similar degradation can be driven by thermally, and that in both cases, the creation of oxygen vacancies is responsible. A lack of robustness to harsh operating conditions (i.e. UV and/or heat) brings the suitability of unprotected molybdenum oxide in photovoltaic applications into question.
    Original languageEnglish
    Pages (from-to)115502
    Number of pages1
    JournalMaterials Research Express
    Volume4
    Issue number11
    DOIs
    Publication statusPublished - 2017

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    Jorge, M., Cooil, S., Edmonds, M. T., Thomsen, L., Nematollahi, M., Mazzola, F., & Wells, J. W. (2017). Accelerated ageing of molybdenum oxide. Materials Research Express, 4(11), 115502. https://doi.org/10.1088/2053-1591/aa9287