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- Title
Molecular weight dependent vertical composition profiles of PCDTBT:PC<sub>71</sub>BM blends for organic photovoltaics.
- Authors
Kingsley, James W.; Marchisio, Pier Paolo; Hunan Yi; 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.
- Subjects
MOLECULAR weights; MOLECULAR physics; PHYSICAL &; theoretical chemistry; PHOTOVOLTAIC cells; POLYMERS; PARTICLES (Nuclear physics); NUCLEAR physics
- Publication
Scientific Reports, 2014, p1
- ISSN
2045-2322
- Publication type
Article
- DOI
10.1038/srep05286