Role of the interplay between spinodal decomposition and crystal growth in the morphological evolution of crystalline bulk heterojunctions

The stability of organic solar cells is strongly affected by the morphology of the photoactive layers, whose separated crystalline and/or amorphous phases are kinetically quenched far from their thermodynamic equilibrium during the production process. The evolution of these structures during the lif...

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Bibliographic Details
Published in:arXiv.org 2020-02
Main Authors: Ronsin, Olivier J J, Harting, Jens
Format: Article
Language:English
Subjects:
Binary systems
Crystal growth
Crystal structure
Crystallinity
Crystallization
Crystals
Demixing
Domains
Heterojunctions
Liquid phases
Morphology
Organic chemistry
Ostwald ripening
Percolation
Photovoltaic cells
Single crystals
Solar cells
Spinodal decomposition
Stability
Stellar system evolution
Thermodynamic equilibrium
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Summary:The stability of organic solar cells is strongly affected by the morphology of the photoactive layers, whose separated crystalline and/or amorphous phases are kinetically quenched far from their thermodynamic equilibrium during the production process. The evolution of these structures during the lifetime of the cell remains poorly understood. In this paper, a phase-field simulation framework is proposed, handling liquid-liquid demixing and polycrystalline growth at the same time in order to investigate the evolution of crystalline immiscible binary systems. We find that initially, the nuclei trigger the spinodal decomposition, while the growing crystals quench the phase coarsening in the amorphous mixture. Conversely, the separated liquid phases guide the crystal growth along the domains of high concentration. It is also demonstrated that with a higher crystallization rate, in the final morphology, single crystals are more structured and form percolating pathways for each material with smaller lateral dimensions.
ISSN:2331-8422
DOI:10.48550/arxiv.1912.09129