Molecular weight dependent vertical composition profiles of PCDTBT:PC71BM blends for organic photovoltaics

Kingsley, James W.; Marchisio, Pier Paolo; Yi, Hunan; Iraqi, Ahmed; Kinane, Christy J.; Langridge, Sean; Thompson, Richard L.; Cadby, Ashley J.; Pearson, Andrew J.; Lidzey, David G.; Jones, Richard A.L.; Parnell, Andrew J.

Abstract

We have used Soxhlet solvent purification to fractionate a broad molecular weight distribution of the polycarbazole polymer PCDTBT into three lower polydispersity molecular weight fractions. Organic photovoltaic devices were made using a blend of the fullerene acceptor PC71BM with the molecular weight fractions. An average power conversion efficiency of 5.89% (peak efficiency of 6.15%) was measured for PCDTBT blend devices with a number average molecular weight of Mn = 25.5 kDa. There was significant variation between the molecular weight fractions with low (Mn = 15.0 kDa) and high (Mn = 34.9 kDa) fractions producing devices with average efficiencies of 5.02% and 3.70% respectively. Neutron reflectivity measurements on these polymer:PC71BM blend layers showed that larger molecular weights leads to an increase in the polymer enrichment layer thickness at the anode interface, this improves efficiency up to a limiting point where the polymer solubility causes a reduction of the PCDTBT concentration in the active layer.

Citation

Kingsley, J. W., Marchisio, P. P., Yi, H., Iraqi, A., Kinane, C. J., Langridge, S., …Parnell, A. J. (2014). Molecular weight dependent vertical composition profiles of PCDTBT:PC71BM blends for organic photovoltaics. Scientific Reports, 4, Article 5286. https://doi.org/10.1038/srep05286

• Journal Article Type: Article
• Publication Date: Jun 13, 2014
• Deposit Date: Jun 17, 2014
• Publicly Available Date: Jun 18, 2014
• Journal: Scientific Reports
• Publisher: Nature Research
• Peer Reviewed: Peer Reviewed
• Volume: 4
• Article Number: 5286
• DOI: https://doi.org/10.1038/srep05286
• Public URL: https://durham-repository.worktribe.com/output/1425276