The Influence of MoOx Anode Stoicheometry on the Performance of Bulk Heterojunction Polymer Solar Cells |
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Authors: | Jonathan Griffin Darren C. Watters Hunan Yi Ahmed Iraqi David Lidzey Alastair R. Buckley |
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Affiliation: | 1. Department of Physics and Astronomy, University of Sheffield, S3 7RH, UK;2. Department of Chemistry, University of Sheffield, S3 7HF, UK |
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Abstract: | Bulk heterojunction solar cells containing molybdenum oxide hole extracting anode contacts have been fabricated with varying stoicheometry using radio frequency reactive sputtering from a Molybdenum metal target. A blend of the newly synthesised conjugated polymer poly[9‐(heptadecan‐9‐yl)‐9H‐carbazole‐2,7‐diyl‐alt‐(5,6‐bis(octyloxy)‐4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole)‐5,5‐diyl] (PCDTBT‐8) and fullerene [6,6]‐Phenyl‐C71‐butyric acid methyl ester (PC70BM) was used as the photoactive layer and device results show that anodes with greater than 98% Molybdenum (VI) oxide result in peak power conversion efficiencies of 3.7%.The presence of up to 28% of Mo (V) results in no significant reduction in efficiency, however the presence of metallic Mo (IV) and lower oxidation states lead to severe reductions in device performance due to a combination of a large hole extraction energy barrier of approximately 0.9eV and reduced device stability. |
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Keywords: | molybdenum oxide organic photovoltaics oxidation state PCDTBT photoelectron spectroscopy |
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