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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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Autores principales: Ghasemi, Bita, Ševčík, Jakub, Nádaždy, Vojtěch, Végsö, Karol, Šiffalovič, Peter, Urbánek, Pavel, Kuřitka, Ivo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8838540/
https://www.ncbi.nlm.nih.gov/pubmed/35160630
http://dx.doi.org/10.3390/polym14030641
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author Ghasemi, Bita
Ševčík, Jakub
Nádaždy, Vojtěch
Végsö, Karol
Šiffalovič, Peter
Urbánek, Pavel
Kuřitka, Ivo
author_facet Ghasemi, Bita
Ševčík, Jakub
Nádaždy, Vojtěch
Végsö, Karol
Šiffalovič, Peter
Urbánek, Pavel
Kuřitka, Ivo
author_sort Ghasemi, Bita
collection PubMed
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.
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spelling pubmed-88385402022-02-13 Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films Ghasemi, Bita Ševčík, Jakub Nádaždy, Vojtěch Végsö, Karol Šiffalovič, Peter Urbánek, Pavel Kuřitka, Ivo Polymers (Basel) Article 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. MDPI 2022-02-08 /pmc/articles/PMC8838540/ /pubmed/35160630 http://dx.doi.org/10.3390/polym14030641 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Ghasemi, Bita
Ševčík, Jakub
Nádaždy, Vojtěch
Végsö, Karol
Šiffalovič, Peter
Urbánek, Pavel
Kuřitka, Ivo
Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films
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 Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8838540/
https://www.ncbi.nlm.nih.gov/pubmed/35160630
http://dx.doi.org/10.3390/polym14030641
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