Conjugated polymers with polar side chains in bulk heterojunction solar cell devices,

Desta Gedefaw, Yi Zhou, Zaifei Ma, Zewdneh Genene, Stefan Hellstrom, Fengling Zhang, Wendimagegn Mammo, Olle Inganas, Mats R. Andersson

    Research output: Contribution to journalArticlepeer-review

    8 Citations (Scopus)

    Abstract

    The synthesis and characteristics of two alternating polyfluorenes (APFO) is presented. The solar cell device efficiency was found to be dependent on the choice of the processing solvent. Two polymers with polar side chains, namely poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis(3''-(2-(2-methoxyethoxy)ethoxy)phenyl)quinoxaline))] (P1) and poly[2,7-(9,9-bis(2-(2-methoxyethoxy)ethyl)fluorene)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis(3''-(2-(2-methoxyethoxy)-ethoxy)phenyl)quinoxaline))] (P2), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron-acceptor materials, processing solvents and thickness of the active layer. The results show that P1, with a higher molecular weight and good film-forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm-2 and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) mixture using o-dichlorobenzene (o-DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o-DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm-2 and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o-DCB as processing solvent.

    Original languageEnglish
    Pages (from-to)22-30
    Number of pages9
    JournalPolymer International
    Volume63
    Issue number1
    DOIs
    Publication statusPublished - Jan 2014

    Keywords

    • Conjugated polymer
    • Donor-acceptor-donor
    • Polar polymer
    • Power conversion efficiency

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