Low‐Refractive Index Layers in Organic Light‐Emitting Diodes via Electrospray Deposition for Enhanced Outcoupling Efficiencies

Umbach, Thorsten Erich; Röllgen, Stefan; Schneider, Stefan; Klesper, Heike; Umbach, Anne Manuela; Meerholz, Klaus

doi:10.1002/adem.201900897

Cited by 9 publications

(5 citation statements)

References 51 publications

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“…In addition to adopting light extraction techniques, such as microlens arrays (18,19), scattering layers (20,21), and corrugated structures (22,23), raising horizontal dipole ratio ( // ) is a feasible molecular engineering approach to reduce optical loss and enhance  out . Elongating molecular conjugation along the direction of transition dipole moment (24)(25)(26)(27) and expanding molecular plane where the transition dipole moment lies (2,(28)(29)(30) are two major molecule design strategies in the literatures, but often at the cost of sacrificing emission color and efficiency of TADF emitters because of varied internal D-A interaction strength or strong intermolecular interactions in the aggregated state.…”

Section: Introductionmentioning

confidence: 99%

Boosting external quantum efficiency to 38.6% of sky-blue delayed fluorescence molecules by optimizing horizontal dipole orientation

Líu

Yang

et al. 2021

Sci. Adv.

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Section: Introductionmentioning

confidence: 99%

Boosting external quantum efficiency to 38.6% of sky-blue delayed fluorescence molecules by optimizing horizontal dipole orientation

Líu

Yang

et al. 2021

Sci. Adv.

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“…The decrease in refractive index can be helpful in the development of light-emitting diodes (LEDs) and other optoelectronic devices, where it can improve the overall efficiency and performance of the devices. 28,29 ZnO NPs are used as waveguides, 30 so it is essential to understand the dispersion parameters in order to determine the strength of the optical transition interaction in the inter-band. The single oscillator model proposed by the Wemple-DiDomenico (WDD) is used to investigate the dispersion parameters of the refractive index for the ZnO/MWCNTs nanocomposite, in the normal dispersion region: 31…”

Section: Resultsmentioning

confidence: 99%

Tailoring Optoelectronic Properties of ZnO Nanoparticles via Incorporation of Multiwalled Carbon Nanotube Contents on of ZnO/MWCNT Nanocomposites

Al-Asbahi

2023

ECS J. Solid State Sci. Technol.

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The present study demonstrates the tailoring of optoelectronic properties of ZnO nanoparticles (NPs) by adding multi-walled carbon nanotubes (MWCNTs) at different weight ratios. ZnO/MWCNT nanocomposites were successfully prepared using the solution blending method, and the optical spectra of all samples were determined using a UV–vis spectrometer. An increase in the optical absorption coefficient (α) and extinction coefficient (k) was observed with an increase in MWCNT content, resulting in the significant ability to attenuate incident light in ZnO/MWCNT nanocomposites compared to pure ZnO NPs. The optical band gap of pure ZnO NPs decreased from 3.26 eV to 2.58 eV in the ZnO/50 wt% MWCNT nanocomposite. The refractive index values ranged from 1.66 to 1.61 as the wavelength varied between 400 nm and 700 nm. Furthermore, the incorporation of MWCNTs in the ZnO/MWCNT nanocomposite had an impact on various dispersion parameters related to the refractive index. With increasing MWCNT content, the dielectric constant (ε 0) decreased from 2.40 to 1.96, while the mean oscillator wavelength (λ 0) increased from 157.7 nm to 164.2 nm and the oscillator strength (S0) decreased from 5.93 × 10−5 nm−2 to 3.70 × 10−6 nm−2. The localized density of state (N/m*) increased from 7.45 × 1057 to 20.8 × 1057 (m3 Kg) −1, and the long wavelength refractive index (ε ∞) rose from 3.683 to 4.745. Moreover, the plasma frequency (ω p) of the electron exhibited an increase from 2.15 × 1031 to 6.01 × 1031 Hz. These findings highlight the potential of tailoring the optoelectronic properties of ZnO NPs through the incorporation of MWCNTs, paving the way for the development of novel materials with improved optoelectronic characteristics for a wide range of applications.

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“…The reduction in refractive index can benefit the advancement of optoelectronic devices such as LEDs, by improving their overall efficiency and performance. 48,49 Using Sellmeier's model and examining the refractive index spectra, it is possible to calculate the mean oscillator wavelength (λ 0 ) and oscillator strength (S 0 ) of the nanocomposites using the following equation 50 :…”

Section: Refractive Index Studymentioning

confidence: 99%

Studying the optoelectronic properties and emission quenching dynamics of poly‐TPD by incorporating ZnO nanoparticles and multiwalled carbon nanotubes

Al‐Asbahi

2023

J of Applied Polymer Sci

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In this study, the optoelectronic properties and emission dynamic quenching of poly‐TPD were investigated upon incorporating ZnO nanoparticles and multiwalled carbon nanotubes (MWCNTs). A solution blending method was utilized to successfully prepare poly‐TPD incorporated with various contents of ZnO/MWCNT nanocomposites. The optoelectronic properties of the nanocomposites were analyzed using UV–Vis and photoluminescence spectrophotometry. The incorporation of the nanocomposites resulted in a decrease in transmittance, reflectance, and absorption edge, indicating a reduction in the poly‐TPD's bandgap. Parameters such as extinction coefficient, Urbach energy, and charge carrier density also decreased with addition of the nanocomposites, suggesting increased scattering, disorder, and the presence of defect states. The decrease in bandgap from 2.970 to 2.852 eV with increasing the nanocomposite content confirmed the emergence of new electronic states. Furthermore, the nature of the transitions changed from direct allowed for pure poly‐TPD to direct forbidden upon incorporation of the nanocomposites. The inclusion of the nanocomposites also led to a decrease in refractive index and fluorescence intensity. The observed fluorescence quenching primarily exhibited dynamic characteristics, with a Stern–Volmer constant of 5.14 L/g and quenching rate constants surpassing the minimum threshold for efficient quenching. The increase in charge transfer rate constants with the nanocomposite content indicated enhanced quenching efficiency and charge transfer, likely due to the increased surface area and presence of defects. These findings suggest that poly‐TPD incorporated with ZnO/MWCNT nanocomposites displays promising properties for applications in optoelectronic devices.

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Low‐Refractive Index Layers in Organic Light‐Emitting Diodes via Electrospray Deposition for Enhanced Outcoupling Efficiencies

Cited by 9 publications

References 51 publications

Boosting external quantum efficiency to 38.6% of sky-blue delayed fluorescence molecules by optimizing horizontal dipole orientation

Boosting external quantum efficiency to 38.6% of sky-blue delayed fluorescence molecules by optimizing horizontal dipole orientation

Tailoring Optoelectronic Properties of ZnO Nanoparticles via Incorporation of Multiwalled Carbon Nanotube Contents on of ZnO/MWCNT Nanocomposites

Studying the optoelectronic properties and emission quenching dynamics of poly‐TPD by incorporating ZnO nanoparticles and multiwalled carbon nanotubes

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