Fullerene Nucleating Agents: A Route Towards Thermally Stable Photovoltaic Blends |
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Authors: | Camilla Lindqvist Jonas Bergqvist Ching‐Chiao Feng Stefan Gustafsson Olof Bäcke Neil D Treat Céline Bounioux Patrik Henriksson Renee Kroon Ergang Wang Anke Sanz‐Velasco Per Magnus Kristiansen Natalie Stingelin Eva Olsson Olle Inganäs Mats R Andersson Christian Müller |
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Institution: | 1. Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, G?teborg, Sweden;2. Biomolecular and Organic Electronics, Department of Physics, Chemistry and Biology, Link?ping University, Link?ping, Sweden;3. Department of Applied Physics, Chalmers University of Technology, G?teborg, Sweden;4. Department of Materials and Centre for Plastic Electronics, Imperial College London, London, UK;5. Department of Solar Energy and Environmental Physics, Jacob Blaustein Institutes for Desert Research, Ben‐Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben‐Gurion, Israel;6. Department of Microtechnology and Nanoscience – MC2, Chalmers University of Technology, G?teborg, Sweden;7. Institute of Polymer Nanotechnology (INKA), University of Applied Sciences and Arts Northwestern Switzerland (FHNW), Windisch, Switzerland |
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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. |
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Keywords: | conjugated polymer fullerene solar cell nucleating agent thermal stability |
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