Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films
Electronic devices based on polymer thin films have experienced a tremendous increase in their efficiency in the last two decades. One of the critical factors that affects the efficiency of polymer solar cells or light emitting devices is the presence of structural defects that controls non-radiativ...
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| Format: | Article |
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MDPI AG
2022-02-01
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| Series: | Polymers |
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| Online Access: | https://www.mdpi.com/2073-4360/14/3/641 |
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| author | Bita Ghasemi Jakub Ševčík Vojtěch Nádaždy Karol Végsö Peter Šiffalovič Pavel Urbánek Ivo Kuřitka |
| author_facet | Bita Ghasemi Jakub Ševčík Vojtěch Nádaždy Karol Végsö Peter Šiffalovič Pavel Urbánek Ivo Kuřitka |
| author_sort | Bita Ghasemi |
| collection | DOAJ |
| description | Electronic devices based on polymer thin films have experienced a tremendous increase in their efficiency in the last two decades. One of the critical factors that affects the efficiency of polymer solar cells or light emitting devices is the presence of structural defects that controls non-radiative recombination. The purpose of this report is to demonstrate a non-trivial thickness dependence of optoelectronic properties and structure (dis)order in thin conductive poly(9,9-dioctyfluorene-alt-benzothiadiazole), F8BT, polymer films. The UV-Vis absorption spectra exhibited blue shift and peak broadening; significant changes in 0–0 and 0–1 radiative transition intensity was found in photoluminescence emission spectra. The density of state (DOS) was directly mapped by energy resolved-electrochemical impedance spectroscopy (ER-EIS). Satellite states 0.5 eV below the lowest unoccupied molecular orbital (LUMO) band were revealed for the thinner polymer films. Moreover, the decreasing of the deep states density in the band gap manifested an increment in the material structural ordering with increasing thickness. Changes in the ratio between crystalline phases with face-on and edge-on orientation of F8BT chains were identified in the films by grazing-incidence wide angle X-ray scattering technique. A thickness threshold in all investigated aspects of the films at a thickness of about 100 nm was observed that can be attributed to the development of J-H aggregation in the film structure and mutual interplay between these two modes. Although a specific structure–property relationship thickness threshold value may be expected for thin films prepared from various polymers, solvents and under different process conditions, the value of about 100 nm can be generally considered as the characteristic length scale of this phenomenon. |
| first_indexed | 2024-03-09T23:15:35Z |
| format | Article |
| id | doaj.art-6aedffb39aa64243b1c5352e71068c09 |
| institution | Directory Open Access Journal |
| issn | 2073-4360 |
| language | English |
| last_indexed | 2024-03-09T23:15:35Z |
| publishDate | 2022-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Polymers |
| spelling | doaj.art-6aedffb39aa64243b1c5352e71068c092023-11-23T17:37:21ZengMDPI AGPolymers2073-43602022-02-0114364110.3390/polym14030641Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin FilmsBita Ghasemi0Jakub Ševčík1Vojtěch Nádaždy2Karol Végsö3Peter Šiffalovič4Pavel Urbánek5Ivo Kuřitka6Centre of Polymer Systems, Tomas Bata University in Zlin, Tr. Tomase Bati 5678, CZ-760 01 Zlin, Czech RepublicCentre of Polymer Systems, Tomas Bata University in Zlin, Tr. Tomase Bati 5678, CZ-760 01 Zlin, Czech RepublicInstitute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-845 11 Bratislava, SlovakiaInstitute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-845 11 Bratislava, SlovakiaInstitute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-845 11 Bratislava, SlovakiaCentre of Polymer Systems, Tomas Bata University in Zlin, Tr. Tomase Bati 5678, CZ-760 01 Zlin, Czech RepublicCentre of Polymer Systems, Tomas Bata University in Zlin, Tr. Tomase Bati 5678, CZ-760 01 Zlin, Czech RepublicElectronic devices based on polymer thin films have experienced a tremendous increase in their efficiency in the last two decades. One of the critical factors that affects the efficiency of polymer solar cells or light emitting devices is the presence of structural defects that controls non-radiative recombination. The purpose of this report is to demonstrate a non-trivial thickness dependence of optoelectronic properties and structure (dis)order in thin conductive poly(9,9-dioctyfluorene-alt-benzothiadiazole), F8BT, polymer films. The UV-Vis absorption spectra exhibited blue shift and peak broadening; significant changes in 0–0 and 0–1 radiative transition intensity was found in photoluminescence emission spectra. The density of state (DOS) was directly mapped by energy resolved-electrochemical impedance spectroscopy (ER-EIS). Satellite states 0.5 eV below the lowest unoccupied molecular orbital (LUMO) band were revealed for the thinner polymer films. Moreover, the decreasing of the deep states density in the band gap manifested an increment in the material structural ordering with increasing thickness. Changes in the ratio between crystalline phases with face-on and edge-on orientation of F8BT chains were identified in the films by grazing-incidence wide angle X-ray scattering technique. A thickness threshold in all investigated aspects of the films at a thickness of about 100 nm was observed that can be attributed to the development of J-H aggregation in the film structure and mutual interplay between these two modes. Although a specific structure–property relationship thickness threshold value may be expected for thin films prepared from various polymers, solvents and under different process conditions, the value of about 100 nm can be generally considered as the characteristic length scale of this phenomenon.https://www.mdpi.com/2073-4360/14/3/641F8BTthin filmschain orderingJ- and H-aggregatesER-EIS |
| spellingShingle | Bita Ghasemi Jakub Ševčík Vojtěch Nádaždy Karol Végsö Peter Šiffalovič Pavel Urbánek Ivo Kuřitka Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films Polymers F8BT thin films chain ordering J- and H-aggregates ER-EIS |
| title | Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films |
| title_full | Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films |
| title_fullStr | Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films |
| title_full_unstemmed | Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films |
| title_short | Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films |
| title_sort | thickness dependence of electronic structure and optical properties of f8bt thin films |
| topic | F8BT thin films chain ordering J- and H-aggregates ER-EIS |
| url | https://www.mdpi.com/2073-4360/14/3/641 |
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