Improvement of the external extraction efficiency of OLED by using a pyramid array

Tanaka, Shin‐ichi; Kawakami, Yasuyuki; Naito, Yuji

doi:10.1117/12.565202

Cited by 4 publications

(5 citation statements)

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“…[11][12][13] The effect of microlens or pyramid arrays attached to the substrate/air interface for unpixellated, ''uninterrupted'' oleds has been investigated by various authors with the result that the extraction efficiency is increased by such structures by a factor in the range of 1.3 to 1.7. 14,[16][17][18][19][20] References 14 and 15 report an average increase of total light output by a factor of 1.5 with a particular strong enhancement at high angles for white oleds. Nakamura 16) investigates the effect of the index of refraction of the substrate n ¼ 1:5 and 1.72 endowed with microlens arrays but can find no effect of the high index substrate on the extraction efficiency.…”

Section: Review Of the State Of The Artmentioning

confidence: 98%

“…The application of microrefractive structures like arrays of small lenses or pyramids or scattering layers is well documented in the published literature. [11][12][13][14][15][16][17][18][19][20][21][22] Pixellated oleds with ''shaped'' substrates with microrefractive structures aligned on individual oled pixels give an increase in extraction efficiency relative to the unstructured substrate by a factor 2 -3. [11][12][13] The effect of microlens or pyramid arrays attached to the substrate/air interface for unpixellated, ''uninterrupted'' oleds has been investigated by various authors with the result that the extraction efficiency is increased by such structures by a factor in the range of 1.3 to 1.7.…”

Section: Review Of the State Of The Artmentioning

confidence: 99%

“…Peng 17) shows that with high index substrates (n ¼ 1:7) an increase in extraction efficiency by a factor of about 1.7 can be achieved. Tanaka 18) investigates the effect of a pyramid array on a glass substrate and reported an increase in extraction efficiency by a factor of 2 for the forward luminance (cd/m 2 ) and of 1.66 for the total flux (W). These results fall short of simulation results obtained by ray-tracing because the oled stack is assumed to be 100% reflecting.…”

Section: Review Of the State Of The Artmentioning

confidence: 99%

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Light Extraction from Organic Light Emitting Diode Substrates: Simulation and Experiment

Greiner

2007

jjap

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The extraction of light from the glass substrate of bottom emitting organic light emitting diodes by structured substrate surfaces is investigated by modelling and experiment. The angular intensity distribution emitted by the oled into the substrate is taken from measurement or calculation and the extraction enhancement by various microrefractive and scattering outcoupling structures is evaluated by Monte Carlo raytracing and experiment. Diagrams for the characterization of outcoupling structures are presented and discussed. It is concluded that the reflectance of the oled stack ultimately limits the amount of light which can be transferred from the oled through the substrate into air and that the transfer can be increased from about 50% for unstructured to about 80% and more for structured substrates and that the theoretical limit can be reached, e.g., with simple microlens structures. To further increase the efficiency of oleds the light guided and absorbed in the oled stack itself has to be tapped. The influence of the outcoupling structures on the angular light distribution emitted from the substrate into air is also studied.

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Section: Review Of the State Of The Artmentioning

confidence: 98%

Section: Review Of the State Of The Artmentioning

confidence: 99%

Section: Review Of the State Of The Artmentioning

confidence: 99%

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Light Extraction from Organic Light Emitting Diode Substrates: Simulation and Experiment

Greiner

2007

jjap

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“…While such structures are widely applied for inorganic LEDs, which are near ideal point sources, they are generally considered impractical for large OLED lighting panels-one can hardly imagine enclosing a large OLED tile inside an even larger glass or plastic hemisphere. 22,[42][43][44][45] In the micro-array configuration, some of the light hitting the surface of the lenses or prisms will be reflected back into the device (e.g., because the angle of incidence is above the critical angle of total internal reflection). 39,40 Truncated prisms represent a slightly more compact alternative, 41 but ultimately also suffer from being too bulky when applied to large area devices.…”

Section: External Outcoupling Schemesmentioning

confidence: 99%

Recent advances in light outcoupling from white organic light-emitting diodes

2015

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Organic light-emitting diodes (OLEDs) have been successfully introduced to the smartphone display market and have geared up to become contenders for applications in general illumination where they promise to combine efficient generation of white light with excellent color quality, glare-free illumination, and highly attractive designs. Device efficiency is the key requirement for such white OLEDs, not only from a sustainability perspective, but also because at the high brightness required for general illumination, losses lead to heating and may, thus, cause rapid device degradation. The efficiency of white OLEDs increased tremendously over the past two decades, and internal charge-to-photon conversion can now be achieved at ∼100% yield. However, the extraction of photons remains rather inefficient (typically <30%). Here, we provide an introduction to the underlying physics of outcoupling in white OLEDs and review recent progress toward making light extraction more efficient. We describe how structures that scatter, refract, or diffract light can be attached to the outside of white OLEDs (external outcoupling) or can be integrated close to the active layers of the device (internal outcoupling). Moreover, the prospects of using top-emitting metal-metal microcavity designs for white OLEDs and of tuning the average orientation of the emissive molecules within the OLED are discussed.

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“…Recently, there are several reports for enhancing the efficiency of the OLED device using micro/nano structures on its surface. [22][23][24] However, it is difficult to straightly apply into the practical industrial fields because these micro/nano structures were based on polymeric material with a low mechanical strength.…”

Section: Resultsmentioning

confidence: 99%

A Fabrication Method of the Silica-Based Moth-Eye Structures and Its Application to the Organic Light-Emitting Diodes

Yang

Han

Lee

2011

J. Electrochem. Soc.

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For the application of moth-eye patterns to practical optical devices, a novel nano-patterning technique, which can fabricate transparent and robust material based nano patterns through a simple process, needs to be developed, because the moth-eye structures are usually exposed to the outer environment. In this study, silica based moth-eye structures were directly fabricated on a glass substrate by the direct hydrogen silsesquioxane (HSQ) printing and annealing technique. The transmittance of the glass substrate was enhanced by 3-4% in the visible range by the silica moth-eye structures and it was confirmed that the light output efficiency of the green organiclight emitting diode (OLED) was enhanced by 7-9% using the encapsulation glass with the silica moth-eye patterns.

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Improvement of the external extraction efficiency of OLED by using a pyramid array

Cited by 4 publications

References 0 publications

Light Extraction from Organic Light Emitting Diode Substrates: Simulation and Experiment

Light Extraction from Organic Light Emitting Diode Substrates: Simulation and Experiment

Recent advances in light outcoupling from white organic light-emitting diodes

A Fabrication Method of the Silica-Based Moth-Eye Structures and Its Application to the Organic Light-Emitting Diodes

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