Accelerated ageing of molybdenum oxide. (7th November 2017)

• Record Type: Journal Article
• Authors: Jorge, Marina; Cooil, Simon; Edmonds, Mark T; Thomsen, Lars; Nematollahi, Mohammadreza; Mazzola, Federico; Wells, Justin W
• Is Part Of: Materials research express. Volume 4:Number 11(2017)
• Publication Date: 2017-11-07
• Subjects: molybdenum oxide -- photoemission spectroscopy -- synchrotron radiation -- surface science; Materials science -- Research -- Periodicals; Materials science -- Periodicals; 620.11
• DOI: 10.1088/2053-1591/aa9287
• Languages: English
• ISSNs: 2053-1591

Abstract

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.