Dual pattern for enhancing light extraction efficiency of white organic light-emitting diodes

Kim, Kwan; Han, Kyoung Hoon; Kim, Yang Doo; Huh, Daihong; Han, Yoonjay; Lee, Heon; Kim, Jang‐Joo

doi:10.1016/j.orgel.2018.03.011

Cited by 14 publications

(7 citation statements)

References 25 publications

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“…Most processes require vacuum chambers and the manufacturing of large OLEDs is limited. [35][36][37][38][39] In our previous work, 40 we demonstrated an internal scattering layer using a nanoscale random rubbed structure (nRRS) to improve OLED performance using an SU-8 polymer via the rubbing technique. The rubbing technique is commonly used to anchor nematic liquid crystals in a desired orientation.…”

Section: Introductionmentioning

confidence: 99%

Enhancing the optical performance of organic light-emitting diodes using nanoscale random rubbed structure

Shin

Lee

Choi

et al. 2022

Nanomaterials and Nanotechnology

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In this study, we evaluated a nanoscale random rubbed structure (nRRS) used as a scattering layer in organic light-emitting diodes (OLEDs) through an innovative manufacturing method. The rubbing technique, which is conventionally utilized only for liquid crystal alignment, is a manufacturing process with excellent merit in that it can form nanoscale random corrugation in a large area without vacuum equipment even at room temperature, and it is simple and inexpensive. The optimized nRRS, fabricated via rubbing, exhibited a high transmittance of 97.8% and haze of 17.8%, making it suitable as a scattering layer for OLEDs. Owing to its random nature, the scattering effect occurred effectively by rearranging the waveguided light inside the glass substrate. The OLED combined with the optimized nRRS showed a 25.4% improvement in the external quantum efficiency. Additionally, the spectral distortion according to the viewing angle was alleviated, which was confirmed by the negligible difference in the International Commission on Illumination 1931 color space coordinates (∆(x, y) = (0.01, 0.013)). The optical performance of the nRRS–OLED was predicted through a finite-difference time-domain simulation and verified by showing results consistent with those of the fabricated device. This research is expected to be widely applied in many optical devices because it is possible to form a random corrugation on the outside of the device without the difficulty of simply fabricating a beneficial optical structure.

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Section: Introductionmentioning

confidence: 99%

Enhancing the optical performance of organic light-emitting diodes using nanoscale random rubbed structure

Shin

Lee

Choi

et al. 2022

Nanomaterials and Nanotechnology

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“…The modulation of the properties of light (transmittance, reflectance, diffraction, interference, scattering, and absorption) is essential for the production and efficacy of optical devices. Such devices include solar cells [1,2], light-emitting diodes (LEDs) [3,4], meta-lenses [5][6][7], holograms [8,9], and flexible displays [10]. One such manipulation, anti-reflection, can increase device efficiency by reducing the Fresnel reflection caused by refractive index variations [1,11].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of high-transmittance and low-reflectance meter-scale moth-eye film via roll-to-roll printing

Choi²,

Chae

et al. 2020

Nanotechnology

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Anti-reflection technology is a core technology in the field of optoelectronic devices that is used to increase efficiency by reducing reflectance. In particular, the bio-mimetic moth-eye pattern has the advantage of being independent of wavelength, polarization, and angle of incidence. In this study, we fabricated a 1.1 m wide meter-scale moth-eye film using roll-to-roll printing. A uniform moth-eye pattern with a height of 170 nm was formed, which reduced the average reflectance value by 3.2% and increased the average transmittance value by 3.1%, in a wide wavelength range of 400–700 nm. Additionally, the moth-eye film coated with a self-assembled monolayer (SAM) exhibited a contact angle of 140.3°, almost equal to the superhydrophobic angle of 150°. Furthermore, the contact angle, transmittance, and reflectance of the SAM-coated moth-eye film were maintained after an environmental test, which was conducted for 168 h at 60 °C and 80% humidity.

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“…To overcome these causes of light loss, many research groups have studied light-extraction technology. Representative methods include randomly distributed structures 8,9 , photonic crystals 10,11 , scattering layers 12,13 , low-refractive-index grids 14 , micro lens array (MLA) 15–17 , patterned substrate surfaces 18 , corrugated structures 19,20 , high-refractive-index substrates 21 , and micro-cavity structures 22–24 . Although these light-extraction techniques have been reported to improve the efficiency of OLEDs, they have the disadvantages that the fabrication steps are complex and difficult and that they are difficult to apply to actual displays and lighting devices.…”

Section: Introductionmentioning

confidence: 99%

Optical characteristics of refractive-index-matching diffusion layer in organic light-emitting diodes

Park

Kim

Lee

et al. 2019

Sci Rep

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We developed a diffusion layer with a refractive index-matching layer added to a transparent nanoscale polymer-based structure to obtain its effective scattering effects. The diffusion layer had higher haze when the refractive index-matching layer to a higher refractive index was used. This diffusion layer was applied to conventional organic light-emitting diodes (OLEDs) and micro-cavity OLEDs (MC-OLEDs) to evaluate the characteristics. When a diffusion layer was applied to conventional OLEDs, the external quantum efficiency (EQE) was 31.1% higher than that of the device without a diffusion layer due to the reduction of the substrate mode, and the viewing angle characteristic was also improved. Then, when the diffusion layer was applied to the MC-OLEDs, all devices showed similar EQE values regardless of the presence or absence of the diffusion layer, and the viewing-angle-dependent characteristics were greatly improved by the diffusion layer. Furthermore, when the diffusion layer was used with polarizer film, the black color implementation was not affected by the polarizer film, proving that it is applicable to actual OLED display products.

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Dual pattern for enhancing light extraction efficiency of white organic light-emitting diodes

Cited by 14 publications

References 25 publications

Enhancing the optical performance of organic light-emitting diodes using nanoscale random rubbed structure

Enhancing the optical performance of organic light-emitting diodes using nanoscale random rubbed structure

Fabrication of high-transmittance and low-reflectance meter-scale moth-eye film via roll-to-roll printing

Optical characteristics of refractive-index-matching diffusion layer in organic light-emitting diodes

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