Browsing by Author "Pearson, Andrew J."

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    Benzoyl side-chains push the open-circuit voltage of PCDTBT/PCBM solar cells beyond 1 V
    (Amsterdam [u.a.] : Elsevier Science, 2017) Lombeck, Florian; Müllers, Stefan; Komber, Hartmut; Menke, S. Matthew; Pearson, Andrew J.; Conaghan, Patrick J.; McNeill, Christopher R.; Friend, Richard H.; Sommer, Michael
    The synthesis, characterization and solar cell performance of PCDTBT and its highly soluble analogue hexyl-PCDTBT with cross-conjugated benzoyl moieties at the carbazole comonomer are presented. Through the use of both model reactions and time-controlled microwave-assisted Suzuki polycondensation, the base-induced cleavage of the benzoyl group from the polymer backbone has been successfully suppressed. Compared to the commonly used symmetrically branched alkyl motif, the benzoyl substituent lowers the energy levels of PCDTBT as well as the band gap, and consequently increases energy of the charge transfer state in blends with PC71BM. As a result, photovoltaic diodes with high-open circuit voltage of above 1 V are realized.
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    Sub-nanometre resolution imaging of polymer-fullerene photovoltaic blends using energy-filtered scanning electron microscopy
    ([London] : Springer Nature, 2015) Masters, Robert C.; Pearson, Andrew J.; Glen, Tom S.; Sasam, Fabian-Cyril; Li, Letian; Dapor, Maurizio; Donald, Athene M.; Lidzey, David G.; Rodenburg, Cornelia
    The resolution capability of the scanning electron microscope has increased immensely in recent years, and is now within the sub-nanometre range, at least for inorganic materials. An equivalent advance has not yet been achieved for imaging the morphologies of nanostructured organic materials, such as organic photovoltaic blends. Here we show that energy-selective secondary electron detection can be used to obtain high-contrast, material-specific images of an organic photovoltaic blend. We also find that we can differentiate mixed phases from pure material phases in our data. The lateral resolution demonstrated is twice that previously reported from secondary electron imaging. Our results suggest that our energy-filtered scanning electron microscopy approach will be able to make major inroads into the understanding of complex, nano-structured organic materials.