Polarized Emission from Conjugated Polymer Chains Aligned by Epitaxial Growth during Off-Center Spin-Coating

Anzai, Takuya; Porzio, William; Vohra, Varun

doi:10.1155/2017/8637108

Cited by 3 publications

(1 citation statement)

References 20 publications

(28 reference statements)

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“…Note that long range order is a quite desirable property for obtaining high and anisotropic charge mobility . Preferential orientation on scales of millimeters and larger can be induced for some CPs using external stimulus, including deposition on a liquid substrate, mechanical rubbing, epitaxial growth and unidirectional deposition techniques, in situ photo-polymerization on nematic liquid crystals, and other methods. The morphology of polycrystalline polymer films has been studied by scanning probe near-field optical microscopy, polarized charge modulation spectroscopy, transmission electron microscopy, near edge X-ray absorption fine structure, and scanning transmission X-ray microscopy. , …”

Section: Introductionmentioning

confidence: 99%

Photo-Oxidation Reveals H-Aggregates Hidden in Spin-Cast-Conjugated Polymer Films as Observed by Two-Dimensional Polarization Imaging

Shi

Xia

et al. 2019

Chem. Mater.

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Spin-cast intermolecular interactions in conjugated polymer films lead to the formation of excited states delocalized over a few oriented and tightly packed conjugated segments. The optoelectronic properties of conjugated polymers are strongly dependent on the presence of such oriented domains at a nanoscale level. We observe oriented domains as large as several micrometers in size spontaneously formed in spin-cast PBDT-TPD films. Two-dimensional polarization imaging of fresh and photodegraded films showed a much higher visibility of the oriented domains in the degraded samples. We propose that the film is a mixture of two phases with different degrees of chain alignment. The photoluminescence of the more anisotropic phase is more stable against photodegradation in comparison with the less anisotropic phase. Photodegradation predominately quenches photoluminescence of the less anisotropic phase making the oriented domains more visible in the polarization contrasts. Spectral and energy transfer properties of the more oriented phase allowed us to assign it to weakly coupled H-aggregates with the suppressed 0−0 vibronic transition. Stable photoluminescence of H-aggregates in comparison with that of nonaggregated (less oriented) chains may help to understand degradation mechanisms of polymer devices and shows the role of energy transfer in this process. Selective degradation-induced quenching can reveal hidden inhomogeneity of conjugated polymer films.

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Section: Introductionmentioning

confidence: 99%

Photo-Oxidation Reveals H-Aggregates Hidden in Spin-Cast-Conjugated Polymer Films as Observed by Two-Dimensional Polarization Imaging

Shi

Xia

et al. 2019

Chem. Mater.

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Semiconductor nanomaterial-based polarized light emission: From materials to light emitting diodes

Fang

Zhang

et al. 2023

Sci. China Mater.

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The overall optical efficiency of backlight-based liquid crystal displays (LCDs) is less than 5% due to the loss of backlight source by polarizers, color filter, liquid crystal layer and so on. Self-emissive light emitting diodes (LEDs) have been undergoing huge development due to their substantial market potentials to meet the demand of future display. More importantly, the polarized LEDs could enhance the energy utilization efficiency by avoiding light loss caused by polarizers. Therefore, it is desirable to look for effective methods to assemble high-quality anisotropic nanomaterial films so as to fabricate polarized LEDs with high degree of polarization and external quantum efficiency. Here, the photoelectrical properties of some semiconductor nanomaterials and their potential applications for polarized LEDs are introduced. The research progress in the field of polarized light emission from materials to films and then to LEDs is reviewed. Mechanisms of polarized emission, and different assembly strategies for polarized light emitting films and LEDs are also summarized and compared. Finally, several current challenges are discussed, and perspectives on future potential commercial application of polarized LEDs are offered. We hope this review will provide a valuable summary on current status and stimulate some new insightful ideas for future development of polarized LEDs.

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Real-time measurement of dynamic evolution of absorption and emission properties of chromophores in single conjugated polymer molecules

Shi¹,

Li²,

Zhou³

et al. 2019

Acta Phys. Sin.

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Conjugated polymers have been widely used in optical sensors, light-emitting diodes and solar cells, due to their attractive optical and semiconducting properties. It is widely accepted that the optical and electrical properties of conjugated polymer molecules depend on the conjugated segments, i.e., chromophores in conjugated polymer molecule. The study of the evolution of the absorption and emission properties of single conjugated polymer molecules is essential to provide complementary information for the influence of conformation of conjugated polymer on its energy transfer process, as well as on the performance of optoelectronic devices based on conjugated polymers. Although the extensive studies have been reported to elucidate the optical properties of conjugated polymers with single molecule spectroscopy, simultaneous revealing their absorption and emission properties and their real-time evolution are rarely reported. In this paper, we simultaneously measure the absorption and emission properties of chromophores in single Poly[2,7-(9,9-dioctylfluorene)-<i>alt</i>-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole](PFO-DBT) conjugated polymer molecules and their real-time evolution by frequency-domain reconstructed defocused wide-field imaging. The emission dipole orientation of chromophore is achieved by applying defocused wide-field fluorescence imaging. The change of defocused patterns of individual polymer chain describes the angular distribution of emitted light and thus the emitting dipole orientation. Meanwhile, the absorption dipole orientation of chromophore in single conjugated PFO-DBT polymer molecule can be clarified in reconstructed frequency-domain imaging by modulating the relative phase of the pulse pairs and performing Fourier transform to the photoluminescence response. The population density of excited state of absorbing chromophore depends both on the relative phase between the ultrashort pulse pairs and on the orientation of absorption transition dipole moment of the chromophore. By extracting the frequency-domain information of fluorescence that is proportional to the population density of excited state, the evolution of absorption dipole orientation of chromophore can be derived. We distinguish three cases for the evolution of chromophores of single PFO-DBT conjugated polymer molecules: the absorption and emission chromophores both keep constant in single PFO-DBT conjugated polymer molecules; one of the dipole orientations of absorption and emission changes, while the other remains unchanged; both of them change simultaneously. The results may pave the way for the further understanding of the role of conformation in the energy transfer pathway in both natural and artificial light harvesting systems at nano- and micro-level.

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Polarized Emission from Conjugated Polymer Chains Aligned by Epitaxial Growth during Off-Center Spin-Coating

Cited by 3 publications

References 20 publications

Photo-Oxidation Reveals H-Aggregates Hidden in Spin-Cast-Conjugated Polymer Films as Observed by Two-Dimensional Polarization Imaging

Photo-Oxidation Reveals H-Aggregates Hidden in Spin-Cast-Conjugated Polymer Films as Observed by Two-Dimensional Polarization Imaging

Semiconductor nanomaterial-based polarized light emission: From materials to light emitting diodes

Real-time measurement of dynamic evolution of absorption and emission properties of chromophores in single conjugated polymer molecules

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