Efficiency enhancement of flexible organic light-emitting devices by using antireflection nanopillars

Ho, Yu‐Hsuan; Liu, Chung-Chun; Liu, Shun‐Wei; Liang, Hsun; Chu, Chia‐Chi; Wei, Pei‐Kuen

doi:10.1364/oe.19.00a295

Cited by 21 publications

(18 citation statements)

References 27 publications

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“…Note that the signal improvements of both SERS and fluorescence are higher than the expected values (∼7.7%) from transmittance improvement through the GNA during both the excitation and the collection process. This substantial improvement can be explained by the following reasons; both light coupling and extraction efficiency through the ARS increase with the incident angle, compared with those from the flat surface . This angular dependency directly contributes to both the excitation and the collection light through a microscope objective.…”

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confidence: 99%

Biologically Inspired Biophotonic Surfaces with Self‐Antireflection

Kim

Jeong

2014

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with interstitial medium can be considered as single-layer ARS. Based on the Maxwell Garnett model, [ 5 ] the self-antirefl ection can be realized by using the spontaneous index modulation of ARS, i.e., medium-fi lled GNA with ∼0.5 FF, at both air-substrate ( n air and n sub ) and solution-substrate ( n sol and n sub ) interfaces, where a surrounding medium with an index ranging from 1.0 to 1.8 completely fi lls the interstitial gaps between the nanopillars. As a result, the effective index naturally meets an antirefl ection condition (Supporting Information Figure S2). The biophotonic surfaces exhibit diverse examples such as antirefl ective substrates with single-side GNA (SS-GNA) and double-side GNA (DS-GNA) or nanoplasmonic surfaces for highly sensitive fl uorescence sensing or surface enhanced Raman scattering (SERS) as well as high contrast imaging (Figure 1 c).A wafer-level nanofabrication of GNA with self-antirefl ection was done by using thin silver fi lm annealing and reactive ion etching (RIE) on a borosilicate glass substrate (n≈1.47). Thermal annealing transforms thin silver fi lm into size-controllable silver nanoislands, which serve as an etching mask for nanopillar formation during the RIE process. Note that the FF of GNA was precisely controlled with the density of Ag nanoislands depending on the initial thickness of thin silver fi lm. This method was applied on both sides of the glass wafer, where the top-side GNA can also be further functionalized as plasmonic nanostructures by evaporating thin silver or gold fi lm ( Figure 2 a). The GNA were etched down by a quarter-wavelength to suppress specular refl ection at air-substrate interface. The effective index for 0.5 ± 0.01 FF GNA with 130 nm in nanopillar height naturally varies from 1.22 to 1.64 for 1.0 to 1.8 in surrounding index, close to the geometric mean of substrate and surrounding indices, i.e., an ideal antirefl ection condition at the interface (Supporting Information Figure S2). In experiment, the maximum transmission through the SS-GNA is clearly shown at 130 nm in nanopillar height, which improves transmission by ∼3.8 percent at air-substrate interface, compared with the fl at surface (Figure 2 b). The DS-GNA remarkably double the transmission improvement, which shows transmittance over 99 percent. In particular, the size distribution of GNA offers broadband antirefl ection in a visible range from 485 nm to 655 nm. The optical images show specular refl ections from fl at surfaces, SS-GNA, and DS-GNA on 4-inch glass wafers, respectively (Figure 2 b). The DS-GNA provides a clear image of the letters whereas those behind the fl at surfaces are visually unreadable due to the substantial specular refl ection.

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confidence: 99%

Biologically Inspired Biophotonic Surfaces with Self‐Antireflection

Kim

Jeong

2014

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“…It is therefore not surprising that the work focused on the improvements of the light extraction by eliminating the SPPs mode, substrate mode, and WG mode in organic layers. Integrating the internal or external micro/nanostructures has demonstrated an effective approach to improve the light extraction efficiency of FOLEDs . In case of the internal micro/nanostructures, they are fabricated on a substrate or holes injection layer for an instance of PEDOT:PSS, and then replicate to atop organic materials and electrode layer by layer.…”

Section: Efficiency Improvement Of Flexible Organic Light‐emitting Dementioning

confidence: 99%

Recent Developments in Flexible Organic Light‐Emitting Devices

Liu

Feng

et al. 2018

Adv Materials Technologies

117

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wearable displays, and conceptual lighting panels. In addition, besides the excellent designs, a flexible OLED (FOLED) [7, has several other advantages, the displays and lighting panels are thinner, lighter, more cost effective, shatterproof, and durable compared to glass or silicon based OLEDs. They are impact resistance and less prone to break than glass. At present, both flexible displays and lighting panels are being mass produced (Samsung and LG on displays, LG and Konica Minolta on lighting). FOLEDs are becoming most promising and popular next-generation display technology in consumer electronics and lighting panels.In order to develop the FOLEDs and realize their practical application, many great efforts have been conducted. The key components of the FOLEDs are flexible substrate, bottom and top electrode, organic functional layers, encapsulation layer, and optional light extraction layers. Differed from conventional OLEDs on rigid glass or silicon substrate, FOLEDs are fabricated on flexible substrates. Up to now, metal foil, flexible glass, and plastic film have been commonly used as flexible substrates for FOLEDs. On the other hand, actual fabric materials, natural silk fibroin films, bacterial cellulose, and rubbery poly (urethane acrylate) have also been developed to achieve the requirements of wearable and stretchable displays. The electrode is also very important for FOLEDs. Compared with the top electrode, more research has been conducted on the bottom electrode because its surface roughness, conductivity, and transmittance for bottom emitting OLEDs play a key role in the performance of FOLEDs. As conventional indiumtin-oxide (ITO) is not suitable for flexible devices as it is brittle, many great alternatives such as thin metal film, conducting polymer, dielectric-metal-dielectric (DMD) multilayers, metal nanowires, graphene, carbon nanotubes (CNTs), and their compound have been studied. It should be mentioned that the performance of organic layers has almost no difference with rigid OLEDs because of their inherent excellent ductility and identical working mechanism. Moreover, for practical and commercial applications, stability and efficiency are two factors of crucial importance. As a consequence, the encapsulation technique and light extraction of FOLEDs are also two research hotspots in recent years. This review will summarize the key components, discuss the method of implementation, highlight the recent research progresses, and conclude the challenges and prospects of FOLEDs. demand for display technology in consumer electronics and lighting panels increases, thin, light, high-quality, and more cost-effective light-emitting devices are required. Organic light-emitting devices (OLEDs), satisfying the criteria exactly, have been considered the most promising next-generation display and lighting technique. In particular, an OLED based on flexible substrate enables the device to be applied to curved displays, electronic newspapers, wearable displays, and conceptual lighting panels, has been alwa...

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“…One species of the polyfluorene family, called Green B, has been used for active layer in traditional organic LEDs or high-performance polymer LEDs [35]- [37]. In organic LEDs, it also shows great mechanical and electrical properties.…”

Section: Introductionmentioning

confidence: 99%

Excellent Color Quality of White-Light-Emitting Diodes by Embedding Quantum Dots in Polymers Material

Lin

Wang

Lin

et al. 2016

IEEE J. Select. Topics Quantum Electron.

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This study employs the polyfluorene composite (called Green B) with several colors of quantum dots to generate the highcolor-rendering index (CRI) white LEDs. The Green B polymer is a good candidate to manufacture the hybrid w-LED because of its good quantum efficacy. The hybrid w-LEDs are fabricated by the mixing of Green B with yellow quantum dots and red quantum dots or orange quantum dots to obtain the correlated color temperatures of 3500 and 5500 K. The use of the hybrid polymer/QDs w-LEDs is proved to be beneficial as QD w-LEDs can improve the CRI up to 90 in 3500 K. The luminous efficiency of such devices can be as high as 17.2l m/W. Index Terms-Light-emitting diodes (LEDs), quantum dots (QDs).

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Efficiency enhancement of flexible organic light-emitting devices by using antireflection nanopillars

Cited by 21 publications

References 27 publications

Biologically Inspired Biophotonic Surfaces with Self‐Antireflection

Biologically Inspired Biophotonic Surfaces with Self‐Antireflection

Recent Developments in Flexible Organic Light‐Emitting Devices

Excellent Color Quality of White-Light-Emitting Diodes by Embedding Quantum Dots in Polymers Material

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