Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films
We present an extensive study of the optical and electronic properties of TIPS-pentacene thin films utilizing in situ x-ray diffraction, polarized optical spectroscopy, and ab initio density functional theory. The influence of molecular packing on the properties are reported for thin films deposited...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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American Physical Society
2020-08-01
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| Series: | Physical Review Research |
| Online Access: | http://doi.org/10.1103/PhysRevResearch.2.033294 |
| _version_ | 1797211319100768256 |
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| author | Yang Li Jing Wan Detlef-M. Smilgies Richards Miller Randall L. Headrick |
| author_facet | Yang Li Jing Wan Detlef-M. Smilgies Richards Miller Randall L. Headrick |
| author_sort | Yang Li |
| collection | DOAJ |
| description | We present an extensive study of the optical and electronic properties of TIPS-pentacene thin films utilizing in situ x-ray diffraction, polarized optical spectroscopy, and ab initio density functional theory. The influence of molecular packing on the properties are reported for thin films deposited in the temperature range from 25^{∘}C to 140^{∘}C and for films that are strain stabilized at their as-deposited lattice spacings after cooling to room temperature. Anisotropic thermal expansion causes relative displacement of neighboring molecules while maintaining a nearly constant stacking distance. This leads to a large blueshift in the absorption spectrum as the temperature increases. The blueshift largely reverses a redshift at room temperature compared to the solution absorption spectrum. A reduction in the ratio of the first two vibronic peaks relative to the solution spectrum is also observed. This combination of electronic and vibronic effects is a signature of charge transfer excitonic coupling with a positive coupling constant J_{CT}, which depends sensitively on the alignment of the nodes of the frontier molecular orbitals with those on neighboring molecules. These effects are also correlated with the sign and magnitude of electron and hole charge transfer integrals t_{e} and t_{h} calculated from density functional theory that provide additional evidence for charge transfer mediated coupling, as well as insight into the origin of an experimentally observed enhancement of the field-effect transistor mobility in strain-stabilized thin films. The results suggest approaches to improve carrier mobility in strained thin films and for optical monitoring of electronic changes. |
| first_indexed | 2024-04-24T10:24:36Z |
| format | Article |
| id | doaj.art-29abff2c32e746c3b9802654bb368ead |
| institution | Directory Open Access Journal |
| issn | 2643-1564 |
| language | English |
| last_indexed | 2024-04-24T10:24:36Z |
| publishDate | 2020-08-01 |
| publisher | American Physical Society |
| record_format | Article |
| series | Physical Review Research |
| spelling | doaj.art-29abff2c32e746c3b9802654bb368ead2024-04-12T16:59:24ZengAmerican Physical SocietyPhysical Review Research2643-15642020-08-012303329410.1103/PhysRevResearch.2.033294Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin filmsYang LiJing WanDetlef-M. SmilgiesRichards MillerRandall L. HeadrickWe present an extensive study of the optical and electronic properties of TIPS-pentacene thin films utilizing in situ x-ray diffraction, polarized optical spectroscopy, and ab initio density functional theory. The influence of molecular packing on the properties are reported for thin films deposited in the temperature range from 25^{∘}C to 140^{∘}C and for films that are strain stabilized at their as-deposited lattice spacings after cooling to room temperature. Anisotropic thermal expansion causes relative displacement of neighboring molecules while maintaining a nearly constant stacking distance. This leads to a large blueshift in the absorption spectrum as the temperature increases. The blueshift largely reverses a redshift at room temperature compared to the solution absorption spectrum. A reduction in the ratio of the first two vibronic peaks relative to the solution spectrum is also observed. This combination of electronic and vibronic effects is a signature of charge transfer excitonic coupling with a positive coupling constant J_{CT}, which depends sensitively on the alignment of the nodes of the frontier molecular orbitals with those on neighboring molecules. These effects are also correlated with the sign and magnitude of electron and hole charge transfer integrals t_{e} and t_{h} calculated from density functional theory that provide additional evidence for charge transfer mediated coupling, as well as insight into the origin of an experimentally observed enhancement of the field-effect transistor mobility in strain-stabilized thin films. The results suggest approaches to improve carrier mobility in strained thin films and for optical monitoring of electronic changes.http://doi.org/10.1103/PhysRevResearch.2.033294 |
| spellingShingle | Yang Li Jing Wan Detlef-M. Smilgies Richards Miller Randall L. Headrick Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films Physical Review Research |
| title | Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films |
| title_full | Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films |
| title_fullStr | Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films |
| title_full_unstemmed | Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films |
| title_short | Enhancement of charge transfer in thermally-expanded and strain-stabilized TIPS-pentacene thin films |
| title_sort | enhancement of charge transfer in thermally expanded and strain stabilized tips pentacene thin films |
| url | http://doi.org/10.1103/PhysRevResearch.2.033294 |
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