Accelerated ageing of molybdenum oxide

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

    Research output: Contribution to journalArticleAcademicpeer-review

    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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    Molybdenum oxide
    Aging of materials
    Degradation
    Ionizing radiation
    Oxygen vacancies
    Electronic properties
    Heating
    X rays

    Cite this

    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
    Jorge, Marina ; Cooil, Simon ; Edmonds, Mark T. ; Thomsen, Lars ; Nematollahi, Mohammadreza ; Mazzola, Federico ; Wells, Justin W. / Accelerated ageing of molybdenum oxide. In: Materials Research Express. 2017 ; Vol. 4, No. 11. pp. 115502.
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    Jorge, M, Cooil, S, Edmonds, MT, Thomsen, L, Nematollahi, M, Mazzola, F & Wells, JW 2017, 'Accelerated ageing of molybdenum oxide' Materials Research Express, vol. 4, no. 11, pp. 115502. https://doi.org/10.1088/2053-1591/aa9287

    Accelerated ageing of molybdenum oxide. / Jorge, Marina; Cooil, Simon; Edmonds, Mark T.; Thomsen, Lars; Nematollahi, Mohammadreza; Mazzola, Federico; Wells, Justin W.

    In: Materials Research Express, Vol. 4, No. 11, 2017, p. 115502.

    Research output: Contribution to journalArticleAcademicpeer-review

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    AU - Jorge, Marina

    AU - Cooil, Simon

    AU - Edmonds, Mark T.

    AU - Thomsen, Lars

    AU - Nematollahi, Mohammadreza

    AU - Mazzola, Federico

    AU - Wells, Justin W.

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    AB - 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.

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