Fullerene Nucleating Agents: A Route Towards Thermally Stable Photovoltaic Blends

Camilla Lindqvist, Jonas Bergqvist, Ching-Chiao Feng, Stefan Gustafsson, Olof Backe, Neil Treat, Celine Bounioux, Patrik Henriksson, Renee Kroon, Ergang Wang, Anke Sanz-Velasco, Per Kristiansen, Natalie Stingelin, Eva Olsson, Olle Inganas, Mats R. Andersson, Christian Muller

    Research output: Contribution to journalArticlepeer-review

    50 Citations (Scopus)

    Abstract

    The bulk-heterojunction nanostructure of non-crystalline polymer:fullerene blends has the tendency to rapidly coarsen when heated above its glass transition temperature, which represents an important degradation mechanism. We demonstrate that fullerene nucleating agents can be used to thermally arrest the nanostructure of photovoltaic blends that comprise a non-crystalline thiophene-quinoxaline copolymer and the widely used fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). To this end, C60 fullerene is employed to efficiently nucleate PCBM crystallization. Sub-micrometer-sized fullerene crystals are formed when as little as 2 wt% C60 with respect to PCBM is added to the blend. These reach an average size of only 200 nanometers upon introduction of more than 8 wt% C60. Solar cells based on C60-nucleated blends indicate significantly improved thermal stability of the bulk-heterojunction nanostructure even after annealing at an elevated temperature of 130 °C, which lies above the glass transition temperature of the blend. Moreover, we find that various other compounds, including C70 fullerene, single-walled carbon nanotubes, and sodium benzoate, as well as a number of commercial nucleating agents - commonly used to clarify isotactic polypropylene - permit to control crystallization of the fullerene phase. Fullerene nucleating agents are used to thermally arrest the nanostructure of photovoltaic blends that comprise a non-crystalline thiophene-quinoxaline copolymer and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). In particular, C60 efficiently nucleates PCBM crystallization and reduces the size of fullerene crystals to only 200 nanometers. Solar cells show significantly improved thermal stability of the bulk-heterojunction nanostructure even after annealing at an elevated temperature of 130 °C.

    Original languageEnglish
    Article number1301437
    Pages (from-to)Art: 1301437
    Number of pages10
    JournalAdvanced Energy Materials
    Volume4
    Issue number9
    DOIs
    Publication statusPublished - 24 Jun 2014

    Keywords

    • conjugated polymer
    • fullerene
    • nucleating agent
    • solar cell
    • thermal stability

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