Influencing Optical and Charge Transport Properties by Controlling the Molecular Interactions of Merocyanine Thin Films
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arXiv
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2024
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| author | Böhner, Lukas Weitkamp, Philipp Limböck, Thorsten Gildemeister, Nora Fazzi, Daniele Schiek, Manuela Bruker, Ruth Hertel, Dirk Schäfer, Roland Lindfors, Klas Meerholz, Klaus |
| author_facet | Böhner, Lukas Weitkamp, Philipp Limböck, Thorsten Gildemeister, Nora Fazzi, Daniele Schiek, Manuela Bruker, Ruth Hertel, Dirk Schäfer, Roland Lindfors, Klas Meerholz, Klaus |
| contents | In organic semiconductors charge transport typically takes place via slow hopping processes. Molecular aggregation can lead to enhanced exciton and charge transport through coupling of the transition dipole moments. In this work, we investigate the optical, morphological, and electronic properties of thin films of a merocyanine dye, that aggregates due to its high ground-state dipole moment. The degree of aggregation of spin-coated thin films can be easily tuned by thermal annealing. We demonstrate the relationship between charge carrier mobility and the degree of aggregation. The mobility is increased by approximately three orders of magnitude due to aggregation. We combine variable angle spectroscopic ellipsometry and polarization-resolved absorption spectroscopy with density functional theory to demonstrate that the aggregated molecules are oriented in an upright, standing configuration relative to the substrate surface. This arrangement involves a co-facial orientation of the molecular pi-systems which is advantageous for lateral charge transport. By utilizing highly oriented pyrolytic graphite as an ordered substrate, we are able to template the growth of the merocyanine layer in vapor phase deposition, and to improve the in-plane morphological order drastically. By correlating atomic force microscopy and photoluminescence microspectroscopy we observe oriented domains of 100s of μm^2 in size, emitting linearly polarized light, whereby maintaining the edge-on molecular arrangement. This promises a further significant enhancement of lateral charge carrier mobility. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_08333 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Influencing Optical and Charge Transport Properties by Controlling the Molecular Interactions of Merocyanine Thin Films Böhner, Lukas Weitkamp, Philipp Limböck, Thorsten Gildemeister, Nora Fazzi, Daniele Schiek, Manuela Bruker, Ruth Hertel, Dirk Schäfer, Roland Lindfors, Klas Meerholz, Klaus Materials Science In organic semiconductors charge transport typically takes place via slow hopping processes. Molecular aggregation can lead to enhanced exciton and charge transport through coupling of the transition dipole moments. In this work, we investigate the optical, morphological, and electronic properties of thin films of a merocyanine dye, that aggregates due to its high ground-state dipole moment. The degree of aggregation of spin-coated thin films can be easily tuned by thermal annealing. We demonstrate the relationship between charge carrier mobility and the degree of aggregation. The mobility is increased by approximately three orders of magnitude due to aggregation. We combine variable angle spectroscopic ellipsometry and polarization-resolved absorption spectroscopy with density functional theory to demonstrate that the aggregated molecules are oriented in an upright, standing configuration relative to the substrate surface. This arrangement involves a co-facial orientation of the molecular pi-systems which is advantageous for lateral charge transport. By utilizing highly oriented pyrolytic graphite as an ordered substrate, we are able to template the growth of the merocyanine layer in vapor phase deposition, and to improve the in-plane morphological order drastically. By correlating atomic force microscopy and photoluminescence microspectroscopy we observe oriented domains of 100s of μm^2 in size, emitting linearly polarized light, whereby maintaining the edge-on molecular arrangement. This promises a further significant enhancement of lateral charge carrier mobility. |
| title | Influencing Optical and Charge Transport Properties by Controlling the Molecular Interactions of Merocyanine Thin Films |
| topic | Materials Science |
| url | https://arxiv.org/abs/2410.08333 |