Thermocleavable Materials for Polymer Solar Cells with High Open Circuit Voltage-A Comparative Study

Thomas Tromholt, Suren Gevorgyan, Mikkel Jørgensen, Frederik C Krebs, Kristian O. Sylvester-Hvid

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The search for polymer solar cells giving a high open circuit voltage was conducted through a comparative study of four types of bulk-heterojunction solar cells employing different photoactive layers. As electron donors the thermo-cleavable polymer poly-(3-(2-methylhexyloxycarbonyl)dithiophene) (P3MHOCT) and unsubstituted polythiophene (PT) were used, the latter of which results from thermo cleaving the former at 310 °C. As reference, P3HT solar cells were built in parallel. As electron acceptors, either PCBM or bis-[60]PCBM were used. In excess of 300 solar cells were produced under as identical conditions as possible, varying only the material combination of the photo active layer. It was observed that on replacing PCBM with bis[60]PCBM, the open circuit voltage on average increased by 100 mV for P3MHOCT and 200 mV for PT solar cells. Open circuit voltages approaching 1 V were observed for the PT:bis[60]PCBM solar cells and a maximum conversion efficiency of 1.3% was obtained for solar cells with P3MHOCT:PCBM as the photoactive material. For the reference solar cells maximum efficiencies of 2.1 and 2.4% were achieved for P3HT:PCBM and P3HT:bis[60]PCBM, respectively. Despite special measures taken in terms of substrate design and device processing, a substantial spread in the photovoltaic properties was generally observed. This spread could not be correlated with the optical properties of the solar cells, the thickness of the photo active layer or the electrode deposition conditions of the aluminum top electrode.
    Original languageEnglish
    JournalA C S Applied Materials and Interfaces
    Volume1
    Issue number12
    Pages (from-to)2768-2777
    ISSN1944-8244
    DOIs
    Publication statusPublished - 2009

    Bibliographical note

    This work was supported by the Danish
    Strategic Research Council (DSF 2104-05-0052 and 2104-
    07-0022).

    Keywords

    • Polymer solar cells
    • Solar energy

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