Novel fabrication method of microlens arrays with High OLED outcoupling efficiency

Kim, Hyun Soo; Moon, Seong Il; Hwang, Dong Eui; Jeong, Ki Won; Kim, Chang Kyo; Moon, Dae‐Gyu; Hong, Chinsoo

doi:10.1016/j.optlastec.2015.09.006

Cited by 38 publications

(15 citation statements)

References 35 publications

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“…[ 9a,19 ] For example, Kim et al presented some novel fabrication methods for MLAs and explored the enhancement of the light out‐coupling efficiencies of OLEDs when using MLAs. [ 20 ] Similar to what is happening with solar cells, the function of the MLAs is to reduce the incident angle at the interface by refraction, making it less than the critical angle. Thus, MLAs can reduce the total internal reflection (TIR) loss and enhance light extraction from OLEDs due to their scattering effect on emitted light.…”

Section: Introductionmentioning

confidence: 99%

High‐Throughput and Controllable Fabrication of Soft Screen Protectors with Microlens Arrays for Light Enhancement of OLED Displays

Ding

Lin

Zhao

et al. 2020

Adv Materials Technologies

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systems, [3] integral imaging systems, [4] and optical communication systems, [5] as well as in biomedical imaging applications. [6] In particular, due to the capability of enhancing solar cell photocurrents [7] and the light emission from organic lightemitting diodes (OLEDs), [8] the integration of MLAs has become a promising solution to gathering light sources [9] for practical applications. With the ever-increasing popularity of touch screen handheld electronic devices, the demand for effective touch screen protectors has risen. Currently, the role of the screen protector is to protect the screen from damage, and few studies have focused on improving the brightness to reduce power consumption. Based on managing the incident light paths, implementing MLAs in screen protectors is expected to improve the energy efficiency of the optoelectronic device. The conventional fabrication methods for MLAs are categorized into direct methods, 2D template methods, and 3D mould methods. The direct methods do not require the preparation of a mask or a mould, and the process is relatively simple. Femtosecond lasers are applied to etch concave MLAs directly on flexible substrates, such as polydimethylsiloxane (PDMS), or to print microdroplets of a highly viscous prepolymer at targeted positions to manufacture planoconvex MLAs. [10] Jung and Jeong fabricated MLAs by melting cylindrical polymer micropatterns covered with a plasma-induced fluorocarbon nanofilm. [11] In contrast, 2D template methods are based on soft lithography or the surface-tension-confined technique to limit the lateral size of the MLAs. For example, Liu et al. described a self-assembly approach for the fabrication of TiO 2 MLAs on a chemically patterned substrate defined by microcontact printing. [12] Bi and Li prepared SU-8 MLAs based on the vapor-induced dewetting of SU-8 thin films on lithographic (PDMS) substrates. [13] Li et al. introduced a method for fabricating MLAs with well-controlled curvature by liquid trapping and electro-hydrodynamic deformation in microholes. [14] However, the process to fabricate the limited 2D templates is complicated. On the other hand, 3D mould methods require fabrication of a mould containing the 3D microstructure to accurately define the geometric shape of the MLAs and then produce the final MLAs by means of replication techniques. Zhang et al. produced MLAs by harnessing the surface tension In this work, soft polydimethylsiloxane (PDMS) screen protectors with microlens arrays (MLAs) are fabricated through a feasible high-throughput approach. Based on the lateral size scaling effect during discontinuous dewetting, desired SU-8 convex MLAs with simultaneously controlled focal length (f) and numerical aperture (NA) are produced on a single substrate. A replication technique is employed to prepare PDMS MLAs with the same structure as that of the SU-8 MLAs. The contact angle and other optical parameters of the MLAs can be tuned over a wide range based on the number of sliding times and lateral size. When the diameter of the ML...

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Section: Introductionmentioning

confidence: 99%

High‐Throughput and Controllable Fabrication of Soft Screen Protectors with Microlens Arrays for Light Enhancement of OLED Displays

Ding

Lin

Zhao

et al. 2020

Adv Materials Technologies

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“…However, the external quantum efficiency of OLEDs is only approximately 20% because of light loss at various interfaces. According to ray‐optics and wave‐optics theories, approximately 80% of the generated light is lost in the waveguide mode of the metal oxide (MO) transparent electrode/organic layer, the surface plasmon polariton modes at the metal/organic interface, and the substrate mode at the air/substrate interface …”

Section: Introductionmentioning

confidence: 99%

Internal Light‐Extraction Layers with Different Refractive Indices for Organic Light‐Emitting Diodes

Park

et al. 2019

Physica Status Solidi (a)

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High‐performance organic light‐emitting diodes (OLEDs) require a light‐extraction layer either inside or outside the device. Herein, transparent metal oxides (MOs) of various refractive indices are inserted between the anode and glass as internal light‐extraction layers to improve the efficiency of the OLED device. Optical simulations are performed to reveal the optimal thicknesses for the light‐extraction layer of metal oxides of various refractive indices. Light‐extraction layers of metal oxides with optimized thickness are then used in OLED devices to evaluate the performance of devices. The device with the higher refractive index MO light‐extraction layer tends to show better device performance. Although the internal light‐extraction layer is inserted, the current flow in the device and the color coordinate variation depending on the viewing angle do not change significantly. These results are helpful in the development of optimized internal light‐extraction layers for individual colors and in the development of OLED displays with optimized light‐extraction layers for each pixel.

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“…Different approaches have been adopted with the aim of optimizing light extraction and viewing angle, including micro lens array (MLA) 5 , 11 – 16 , dielectric Bragg gratings 17 – 19 , surface plasmons 20 , buckling patterns 21 , periodic corrugation 8 , low-index grids 22 , and photonic crystals 23 . Methods that modify the internal or external surfaces of the substrate of OLEDs minimize the total internal reflection.…”

Section: Introductionmentioning

confidence: 99%

Simple method for fabricating scattering layer using random nanoscale rods for improving optical properties of organic light-emitting diodes

Kwack

Choi

Park

et al. 2018

Sci Rep

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We investigated a low-temperature mask-free process for preparing random nanoscale rods (RNRs) as a scattering layer. The process involves spin coating and dry etching, which are already widely applied in industry. Our film exhibited 17–33% optical haze at 520 nm wavelength and 95% total transmittance in the visible range. Therefore, this film can be used as a scattering layer for improving viewing angle characteristics and decreasing substrate mode loss in organic light-emitting diodes (OLEDs). Specifically, we focussed on varying the height and density of the RNRs to control the optical characteristics. As a result, the OLEDs with RNRs revealed a variation in colour coordinates of Δ(x, y) = (0.007, 0.014) for a change in the viewing angle, which was superior to those without the RNRs that displayed a variation of Δ(x, y) = (0.020, 0.034) in CIE 1931. Moreover, the OLEDs with RNRs exhibited 31% enhanced external quantum efficiency compared to those of the OLEDs with the bare substrate. The flexibility of the polymer used for the RNRs and the plasma treatment suggests that the RNRs can be applied to flexible OLED displays and lighting systems.

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Novel fabrication method of microlens arrays with High OLED outcoupling efficiency

Cited by 38 publications

References 35 publications

High‐Throughput and Controllable Fabrication of Soft Screen Protectors with Microlens Arrays for Light Enhancement of OLED Displays

High‐Throughput and Controllable Fabrication of Soft Screen Protectors with Microlens Arrays for Light Enhancement of OLED Displays

Internal Light‐Extraction Layers with Different Refractive Indices for Organic Light‐Emitting Diodes

Simple method for fabricating scattering layer using random nanoscale rods for improving optical properties of organic light-emitting diodes

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