An experimental and theoretical study of the structural ordering of the PTB7 polymer at a mesoscopic scale

Urbánek, Pavel; Kuřitka, Ivo; Ševčík, Jakub; Toušková, J.; Toušek, J.; Nádaždy, Vojtěch; Nádaždy, Peter; Végsö, Karol; Šiffalovič, Peter; Rutsch, Radka; Urbánek, Michal

doi:10.1016/j.polymer.2019.02.048

Cited by 14 publications

(12 citation statements)

References 51 publications

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“…Nevertheless, with the increasing thickness, the polymer chains can form a film with a more organized structure and, thus, the H-aggregation with alternating π-stacking of polymer chains is more favorable and changes the spectral features of the material. For the thickest films, the structural ordering of chains causes prevailing 0–1 with longer conjugation length resulting in low energy radiative states [ 16 , 21 ].…”

Section: Resultsmentioning

confidence: 99%

“…This decrease of DOS as a function of film thickness is depicted in Figure 5 b. It can be explained by a general increase in structural ordering of polymer chains and the formation of organized units resulting in the lower population of defect states in the gap [ 21 ].…”

Section: Resultsmentioning

confidence: 99%

“…The competition between the formations of J- and H-aggregates could be the reason for this phenomenon. Based on the aforementioned facts, it appears that there is a thickness threshold in all of the investigated aspects of the PTB7, Poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), and polysilanes thin films [ 21 , 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

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Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films

et al. 2022

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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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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films

et al. 2022

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“…Film thickness can impact on the microstructure of the thin conjugated polymer film and photoluminescence because of the various levels of manifestation of nonlocalized (aggregate states) and localized(intrachain) transitions. With increase of the thickness to some extent more ordered structure can be achieved and there is a thickness threshold in which the mesoscale (between nano-and micro-dimensions) effects such as self-healing mechanism will be revealed [10,11]. The effect of film thickness on optoelectrical properties and the correlation between the thickness and vibronic transition manifestations are presented in this study.…”

Section: Introductionmentioning

confidence: 91%

“…Nevertheless, with increasing thickness, the polymer chains can form a film with a more organized structure, and thus the H-aggregation with alternating π-stacking of polymer chains is more favorable and changes the spectral features of the material. For the thickest films, the structural ordering of chains causes prevailing 0-1 with longer conjugation length resulting in low energy radiative states [4,10].…”

Section: Photoluminescence (Pl) Spectroscopymentioning

confidence: 99%

Polymer chain ordering manifestation in photoluminescence of thin F8BT films

Ghasemi

Ševčík

Urbánek

et al. 2020

NANOCON Conference Proeedings

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Poly(9,9-dioctyfluorene-alt-benzothiadiazole), F8BT, thin films were successfully deposited using spin coating and drop-casting methods on glass and silicon substrates. Films with thicknesses varying from tens to hundreds of nanometers were obtained as a result of variation in the deposition conditions, such as concentration or coating methods. The trends in manifestations of 0-0 and 0-1 vibronic transitions in UV-VIS absorption and photoluminescence (PL) spectra correlate with the thickness of the thin films. A threshold in the intensity ratio of the two transitions was observed at the thin film thickness about 250 nm. The observed spectral features are interpreted in terms of the competitive effects of J-and H-aggregation of the macromolecular chains.

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Releasing Acceptor from Donor Matrix to Accelerate Crystallization Kinetics with a Second Donor toward High‐Efficiency Green‐Printable Organic Photovoltaics

Xue

Zhao

et al. 2023

Adv Funct Materials

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The state‐of‐the‐art power conversion efficiency (PCE) of organic solar cells (OSCs) is typically achieved in the devices fabricated by toxic halogen solvents with complex post‐treatment processes in strictly inert atmosphere. Developing suitable processing method for printing in ambient air using eco‐friendly solvents with continuous solution supply and fabricating efficient devices without any post‐treatment are intensively desired. Controlling the crystallization kinetics to fine‐tune the acceptor's assembly behavior with a second donor for favorable morphological evolution is an effective approach to achieve above requirements. Herein, a kinetics‐controlling strategy is implemented by introducing a strong crystalline small molecule, BTR‐Cl, to enhance the crystallinity of acceptors. The combined in situ spectra characterizations revealed that the earlier aggregation of acceptor and modulation in conformation of PM6 can be achieved. This unique aggregation behavior facilitated enhanced film crystallization with reduced paracrystallinity of π–π stacking, resulting in improved charge transport and inhibited charge recombination. An outstanding PCE of 17.50% is obtained for the device processed with o‐xylene via ambient air printing without any post‐treatment. More significantly, efficient all‐printed inverted devices and large‐area modules are prepared. The generalization of this strategy has been confirmed in other efficient systems, suggesting a great potential for universally fabricating high‐efficiency and eco‐friendly OSCs.

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An experimental and theoretical study of the structural ordering of the PTB7 polymer at a mesoscopic scale

Cited by 14 publications

References 51 publications

Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films

Thickness Dependence of Electronic Structure and Optical Properties of F8BT Thin Films

Polymer chain ordering manifestation in photoluminescence of thin F8BT films

Releasing Acceptor from Donor Matrix to Accelerate Crystallization Kinetics with a Second Donor toward High‐Efficiency Green‐Printable Organic Photovoltaics

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