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Correlating Emissive Non-Geminate Charge Recombination with Photocurrent Generation Efficiency in Polymer/Perylene Diimide Organic Photovoltaic Blend Films

Authors

  • Panagiotis E. Keivanidis,

    Corresponding author
    1. Department of Physics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
    2. Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
    Current affiliation:
    1. Centre for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milan, Italy
    • Department of Physics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK.
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  • Valentin Kamm,

    1. Max Planck Institute for Polymer Research, Max Planck Research Group for Organic Optoelectronics, Ackermannweg 10, 55128, Mainz, Germany
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  • Weimin Zhang,

    1. Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
    2. Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2BW, UK
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  • George Floudas,

    1. Department of Physics, University of Ioannina, 451 10 Ioannina, Greece, Foundation for Research and Technology-Hellas (FORTH-BRI), Greece
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  • Frédéric Laquai,

    1. Max Planck Institute for Polymer Research, Max Planck Research Group for Organic Optoelectronics, Ackermannweg 10, 55128, Mainz, Germany
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  • Iain McCulloch,

    1. Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
    2. Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2BW, UK
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  • Donal D. C. Bradley,

    1. Department of Physics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
    2. Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
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  • Jenny Nelson

    1. Department of Physics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
    2. Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2BZ, UK
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Abstract

Evidence for a correlation between the dynamics of emissive non-geminate charge recombination within organic photovoltaic (OPV) blend films and the photocurrent generation efficiency of the corresponding blend-based solar cells is presented. Two model OPV systems that consist of binary blends of electron acceptor N′-bis(1-ethylpropyl)-3,4,9,10-perylene tetracarboxy diimide (PDI) with either poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) or poly(9,9-dioctylindenofluorene-co-benzothiadiazole) (PIF8BT) as electron donor are studied. For the F8BT:PDI and PIF8BT:PDI devices photocurrent generation efficiency is shown to be related to the PDI crystallinity. In contrast to the F8BT:PDI system, thermal annealing of the PIF8BT:PDI layer at 90 °C has a positive impact on the photocurrent generation efficiency and yields a corresponding increase in PL quenching. The devices of both blends have a strongly reduced photocurrent on higher temperature annealing at 120 °C. Delayed luminescence spectroscopy suggests that the improved efficiency of photocurrent generation for the 90 °C annealed PIF8BT:PDI layer is a result of optimized transport of the photogenerated charge-carriers as well as of enhanced PL quenching due to the maintenance of optimized polymer/PDI interfaces. The studies propose that charge transport in the blend films can be indirectly monitored from the recombination dynamics of free carriers that cause the delayed luminescence. For the F8BT:PDI and PIF8BT:PDI blend films these dynamics are best described by a power-law decay function and are found to be temperature dependent.

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