TY - JOUR
T1 - Accelerated ageing of molybdenum oxide
AU - Jorge, Marina
AU - Cooil, Simon
AU - Edmonds, Mark T.
AU - Thomsen, Lars
AU - Nematollahi, Mohammadreza
AU - Mazzola, Federico
AU - Wells, Justin W.
PY - 2017
Y1 - 2017
N2 - 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.
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.
U2 - 10.1088/2053-1591/aa9287
DO - 10.1088/2053-1591/aa9287
M3 - Article
VL - 4
SP - 115502
JO - Materials Research Express
JF - Materials Research Express
SN - 2053-1591
IS - 11
ER -