Controlling the Crystallinity Development During the Thermal annealing of Polymer:Fullerene Solar Cell Blends

Fatma Demir, Niko Van Den Brande, Sabine Bertho, Eszter Voroshazi, Jean Manca, Dirk Vanderzande, Paul Heremans, Bruno Van Mele, Guy Van Assche

Onderzoeksoutput: Meeting abstract (Book)Research


The active layers used in Organic Photovoltaics (OPV) are often composed of a light absorbing, electron-donating, and hole-conducting polymer, and an electron-accepting and electron-conducting fullerene derivative. These components are blended together to form a phase-separated active layer with a co-continuous nanomorphology, in which both exciton separation and charge transport are optimized [1, 2].
In general, post-production annealing is a necessity to increase the crystallinity of the components and to create conductive pathways for the charges generated at the polymer:fullerene interface to flow towards the corresponding electrodes, thus enhancing the overall device efficiency [3,4]. For an optimal efficiency and performance of the solar cells, a finely-dispersed phase morphology, having 5-20 nm dimensions, is thought to be required [5]. Both for fine-tuning the morphology to increase the solar cell efficiency, and also for retaining the desired morphology during long-term operation, the post-production annealing conditions need to be fine-tuned.
However, optimal conditions for annealing temperatures and times can only be chosen, once the thermal transition temperatures and annealing kinetics of the blends are well-known. Using advanced fast-scanning thermal analysis techniques, the formation of nuclei and growth of crystals during heating or cooling can be avoided, allowing for the study of the fast crystallization processes at the start of the annealing process [6]. The annealing kinetics and the stability of the final morphology will depend on the thermal transition temperatures of the pure components, the phase behaviors of the blends, and the crystallization kinetics of the polymer: fullerene systems.
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[6] Demir, F., Van den Brande, N., Van Mele, B., Bertho, S., Vanderzande, D., Manca, J., and Van Assche, G., Journal of Thermal Analysis and Calorimetry, 845-849 (2011).
Originele taal-2English
TitelBPG 2012, Belgium Polymer Group, Blankenberge, Belgium
StatusPublished - 11 mei 2012


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