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This study utilized cellulose-based external light extraction films to enhance the outcoupling efficiency of organic light-emitting diodes (OLEDs). These films were created through a straightforward fabrication employing the biopolymers hydroxyethyl cellulose (HEC) and tannic acid (TA). We observed that the hydrogen bonding between HEC and TA could spontaneously generate a random microtextured surface on the HEC: TA films. Furthermore, the surface morphology of the HECTA film can be adjusted by varying the TA content. When applying the HECTA films as an external light-extraction layer for OLEDs, we noticed a remarkable improvement in the external quantum efficiency and current efficiency of the OLEDs up to 54% compared to those without the HECTA film. Additionally, the HECTA film displayed an outstanding ability to absorb ultraviolet light. Therefore, it is anticipated that the HECTA film can significantly contribute to prolonging the stability of OLEDs. [ABSTRACT FROM AUTHOR]

The effects of different dielectric outcoupling layers on top‐emitting perovskite light‐emitting diodes (LEDs) are studied. The ability to manipulate light output via index of refraction and thickness variation of the outcoupling layer is demonstrated, leading to 27.7% improvement in external quantum efficiency (EQE) compared to devices without added outcoupling dielectric layers. Optimal dielectric thicknesses are able to be resolved for EQE enhancement across three outcoupling materials with different refractive indices. Optical simulations are shown to agree well with experimental results and allow for future optimization for various perovskite compositions with different emission spectra. [ABSTRACT FROM AUTHOR]

This study utilized cellulose-based external light extraction films to enhance the outcoupling efficiency of organic light-emitting diodes (OLEDs). These films were created through a straightforward fabrication employing the biopolymers hydroxyethyl cellulose (HEC) and tannic acid (TA). We observed that the hydrogen bonding between HEC and TA could spontaneously generate a random microtextured surface on the HEC: TA films. Furthermore, the surface morphology of the HECTA film can be adjusted by varying the TA content. When applying the HECTA films as an external light-extraction layer for OLEDs, we noticed a remarkable improvement in the external quantum efficiency and current efficiency of the OLEDs up to 54% compared to those without the HECTA film. Additionally, the HECTA film displayed an outstanding ability to absorb ultraviolet light. Therefore, it is anticipated that the HECTA film can significantly contribute to prolonging the stability of OLEDs.

Three novel asymmetric Ir(III) complexes have been rationally designed to optimize their emitting dipole orientations (EDO) and enhance light outcoupling in blue phosphorescent organic light‐emitting diodes (OLEDs), thereby boosting their external quantum efficiency (EQE). Bulky electron‐donating groups (EDGs), namely: carbazole (Cz), di‐tert‐butyl carbazole (tBuCz), and phenoxazine (Pxz) are incorporated into the tridentate dicarbene pincer chelate to induce high degree of packing anisotropy, simultaneously enhancing their photophysical properties. Angle‐dependent photoluminescence (ADPL) measurements indicate increased horizontal transition dipole ratios of 0.89 and 0.90 for the Ir(III) complexes Cz‐dfppy‐CN and tBuCz‐dfppy‐CN, respectively. Analysis of the single crystal structure and density functional theory (DFT) calculation results revealed an inherent correlation between molecular aspect ratio and EDO. Utilizing the newly obtained emitters, the blue OLED devices demonstrated exceptional performance, achieving a maximum EQE of 30.7% at a Commission International de l'Eclairage (CIE) coordinate of (0.140, 0.148). Optical transfer matrix‐based simulations confirmed a maximum outcoupling efficiency of 35% due to improved EDO. Finally, the tandem OLED and hyper‐OLED devices exhibited a maximum EQE of 44.2% and 31.6%, respectively, together with good device stability. This rational molecular design provides straightforward guidelines to reach highly efficient and stable saturated blue emission. [ABSTRACT FROM AUTHOR]

Anti‐reflection (AR) characteristics on the display surface and light outcoupling efficiency are significant factors for controlling external and internal light in organic light‐emitting diodes (OLEDs), respectively. This paper presents the fabrication of moth‐eye nanostructured parylene‐C films that simultaneously achieve optimized AR characteristics and enhanced OLED performance. AR performance is optimized by varying the nanostructure dimensions, resulting in a nanostructured film with a reflectance of <1%. Furthermore, applying this nanostructured film to OLEDs improved the light outcoupling efficiency by 40% compared with the reference device. Therefore, employing nanostructured parylene‐C films to enhance the optical characteristics of OLEDs is proposed. [ABSTRACT FROM AUTHOR]

AR, VR Headset for "metaverse" is one of candidates to widen human life experiences with virtual reality. Display requirement for headset is the high resolution as to 3000ppi that needs to enhance outcoupling efficiency of OLED (OLEDoS). We optimized 2D hole arrayed double anode structure for mass production with materials, thickness of anode and interlayer, process variation of etching top anode, and particles in double anodes. Outcoupling efficiency of optimized structure is improved to 1.377 folds than conventional TE‐OLEDs. We hope that this study promotes more approaches to excite SPPs of anode. [ABSTRACT FROM AUTHOR]

Abstract Three novel asymmetric Ir(III) complexes have been rationally designed to optimize their emitting dipole orientations (EDO) and enhance light outcoupling in blue phosphorescent organic light‐emitting diodes (OLEDs), thereby boosting their external quantum efficiency (EQE). Bulky electron‐donating groups (EDGs), namely: carbazole (Cz), di‐tert‐butyl carbazole (tBuCz), and phenoxazine (Pxz) are incorporated into the tridentate dicarbene pincer chelate to induce high degree of packing anisotropy, simultaneously enhancing their photophysical properties. Angle‐dependent photoluminescence (ADPL) measurements indicate increased horizontal transition dipole ratios of 0.89 and 0.90 for the Ir(III) complexes Cz‐dfppy‐CN and tBuCz‐dfppy‐CN, respectively. Analysis of the single crystal structure and density functional theory (DFT) calculation results revealed an inherent correlation between molecular aspect ratio and EDO. Utilizing the newly obtained emitters, the blue OLED devices demonstrated exceptional performance, achieving a maximum EQE of 30.7% at a Commission International de l'Eclairage (CIE) coordinate of (0.140, 0.148). Optical transfer matrix‐based simulations confirmed a maximum outcoupling efficiency of 35% due to improved EDO. Finally, the tandem OLED and hyper‐OLED devices exhibited a maximum EQE of 44.2% and 31.6%, respectively, together with good device stability. This rational molecular design provides straightforward guidelines to reach highly efficient and stable saturated blue emission.

Increasing the internal light extraction efficiency of organic light‐emitting diodes (OLEDs) is key to improving their performance for solid‐state lighting applications; however, it is challenging to do this in a way that is compatible with high volume manufacturing. Here, it is shown that the outcoupling efficiency of OLEDs can be improved by diluting their hole transport layer (HTL) with the low refractive index material trifluoropropyl oligomeric silsesquioxane (F‐POSS). Specifically, co‐evaporating 40 vol.% F‐POSS in the HTL of single and multi‐stack phosphorescent OLEDs decreases its refractive index by Δn ≈ 0.2, which in turn yields a ≈12% increase in their outcoupling efficiency with no impact on electrical performance or operational lifetime. This result is significant because F‐POSS is a small molecule that sublimes cleanly, does not aggregate, and is compatible with state‐of‐the‐art HTL materials, making it a realistic path to increase light extraction in commercial OLEDs manufactured on existing production lines. [ABSTRACT FROM AUTHOR]

Abstract Anti‐reflection (AR) characteristics on the display surface and light outcoupling efficiency are significant factors for controlling external and internal light in organic light‐emitting diodes (OLEDs), respectively. This paper presents the fabrication of moth‐eye nanostructured parylene‐C films that simultaneously achieve optimized AR characteristics and enhanced OLED performance. AR performance is optimized by varying the nanostructure dimensions, resulting in a nanostructured film with a reflectance of

In this study, we demonstrated organic light-emitting diodes (OLEDs) outcoupling with a flexible polydimethylsiloxane (PDMS) film with a micro-convex structure using the breath figure (BF) method. We can easily control the micro-convex pattern by adjusting the concentration of polystyrene and the humidity during the BF process. As process conditions to fabricate the micro-convex structure, polymer concentrations of 10, 20, 40, and 80 mg/mL and 60, 70, and 80% relative humidity were used. To evaluate the optical properties, we analyzed the transmission, diffusion, and electroluminescence with or without the micro-convex structure on the OLEDs. The shape and density of the micro-convex structure are related to its optical properties and outcoupling and we have experimentally demonstrated this. By applying a micro-convex structure, it achieved up to a 42% improvement in the external quantum efficiency compared to bare OLEDs (without any light extraction film). We expect the fabricated flexible light extraction film to be effective for outcoupling and applicable to flexible devices. [ABSTRACT FROM AUTHOR]

We report the improved outcoupling of organic light‐emitting diodes (OLEDs) using flexible micro‐convex‐structured films fabricated by the breath figure method. The light extraction pattern was controlled by the particle size distribution according to the concentration of polystyrene with the solvent evaporation method. The OLEDs assembled with micro‐convex‐structure film presented an efficiency improvement of 36%. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated organic light-emitting diodes (OLEDs) outcoupling with a flexible polydimethylsiloxane (PDMS) film with a micro-convex structure using the breath figure (BF) method. We can easily control the micro-convex pattern by adjusting the concentration of polystyrene and the humidity during the BF process. As process conditions to fabricate the micro-convex structure, polymer concentrations of 10, 20, 40, and 80 mg/mL and 60, 70, and 80% relative humidity were used. To evaluate the optical properties, we analyzed the transmission, diffusion, and electroluminescence with or without the micro-convex structure on the OLEDs. The shape and density of the micro-convex structure are related to its optical properties and outcoupling and we have experimentally demonstrated this. By applying a micro-convex structure, it achieved up to a 42% improvement in the external quantum efficiency compared to bare OLEDs (without any light extraction film). We expect the fabricated flexible light extraction film to be effective for outcoupling and applicable to flexible devices.

Lasing at the nanoscale using plasmonic nanoparticles offers the prospect of strong field concentration, hence strong light−matter interactions, low lasing thresholds, and ultrafast operation. However plasmonic nanoparticles suffer from high dissipative and radiative losses, the latter being rigidly tied to the shape of the nanoparticles and symmetry of their localized plasmon resonant modes. To overcome this limitation, recent theoretical work proposes using direct lasing into dark surface states to construct lasers that conceptually allow for independent implementation of the lasing state and its coherent radiation output. Here, lasing in dark resonant states of a metasurface laser and controllable coherent outcoupling of radiation with the aid of a tightly coupled, weakly radiative metasurface are demonstrated experimentally. The laser is implemented using a thin, low‐loss dielectric film supporting surface mode‐like dark dielectric bound states and the coupling metasurface is composed of small non‐resonant scatterers that controllably but weakly perturb the dark mode and turn it partially bright. Distinct far‐field signatures that can be observed experimentally for both dark and bright lasing are identified and demonstrated. The scalability of this design, here implemented for lasing in the near‐infrared, enables large‐aperture ultra‐thin coherent light sources with controllable emission from the infrared to the visible. [ABSTRACT FROM AUTHOR]

Extracting light from the waveguide mode in organic light‐emitting diodes (OLED) is most challenging as such optical mode is intrinsic in traditional OLED due to materials and layered structure used in the device. This work intends to address the root cause of the light trapping problem. We systematically analyzed OLEDs made with an ultrathin Ag anode and found that waveguide modes can be completely eliminated by designing a structure to below the cutoff thickness of waveguide modes. We also experimentally verified the waveguide mode elimination in organic waveguides. In principle such a scheme can be extended to tandem cells, and in making transparent OLED. A further benefit is the ductility of the ultrathin metal allows foldable OLED to be realized. [ABSTRACT FROM AUTHOR]

Metal halide perovskite light‐emitting diodes (PeLEDs) are regarded as alternative candidates for next‐generation display technologies due to their high efficiency, superior color purity, tunable bandgap. However, the research on transparent and top‐emitting PeLED with Lambertian emission profile significantly lags behind due to optical microcavity effect, which has become one of the main obstacles for potential practical display applications. Here, strategies are developed to suppress the microcavity effect by enhancing the transmission of the semitransparent electrode and extending the optical cavity length. Besides, a nanopatterned structure is incorporated to suppress the surface plasma and waveguide mode effect. Based on the above combination strategies, a transparent PeLED yields a record total external quantum efficiency (EQE) of 16.1% with Lambertian emission by depositing high refractive index molybdenum oxide on the semitransparent cathode. Besides, a high EQE of 13.6% of a top‐emitting device with quasi‐Lambertian emission is achieved by stretching the optical distance between two reflective layers and enhancing the transmission of the semitransparent electrode. The nanopatterned structure enables suppressed waveguide mode and surface plasmon polariton dilapidation of top‐emitting PeLEDs. This work paves a path to design transparent and top‐emitting PeLEDs for potential applications in both traditional and novel transparent displays. [ABSTRACT FROM AUTHOR]

We present the latest status of high performance OLED material development based on conjugated polymer technologies. The material which shows high performance is very suitable for printed OLED panel fabrication. New materials to reduce degradation from exciton realized better device lifetime. New materials which show PL spectrum with narrow line width and suitable peak wavelength have been developed to improve efficiency by enhancing the outcoupling on top‐emission (TE) devices. [ABSTRACT FROM AUTHOR]

Abstract Metal halide perovskite light-emitting diodes (PeLEDs) are emerging as a promising candidate for next-generation optoelectronic devices. The efficiency of PeLEDs has developed explosively in a short time, but their overall efficiency is still low. This is strongly related to the high refractive indexes of indium-tin-oxide (ITO) and perovskite emitting layers. Various outcoupling strategies are being introduced to outcouple the light trapped inside the layers. However, the proposed methods have experimental challenges that need to be overcome for application to large-area electronics. Based on optical simulations, we demonstrate that the thicknesses of the ITO and perovskite layers are key parameters to improve the outcoupling efficiency of PeLEDs. In addition, the optical energy losses of PeLEDs can be reduced significantly by properly adjusting the thicknesses of the two layers. This leads to outstanding optical performance with a maximum EQE greater than 20% without using any other external outcoupling strategies.

Organic light‐emitting diodes (OLEDs) have successfully established themselves as light sources vital in high‐end mobile displays and television due to various advances made for a wide range of technical aspects from materials, devices, and processes to air‐tight packaging and systems. However, a significant portion of the generated excitons in OLEDs are still lost to various channels. Among them, excitation of surface plasmon polaritons (SPPs) is a critical source of exciton loss, the recovery of which often involves structuring in nanoscale. Herein, a nano‐pattern‐free approach is reviewed to reducing SPP loss that makes use of materials with low refractive index. Because of the limited availability of such low refractive index materials, a method to use a low extraordinary refractive index of birefringent organic semiconductors is explored. With the proposed method combined with common lens‐based outcoupling schemes and high refractive index substrates, it is shown that an ultrahigh external quantum efficiency of ≈72% in a green, single‐junction phosphorescent OLED is within the reach. Transient photoluminescence measurement is used to monitor the change in Purcell factor incurred by the use of the birefringent low refractive index layer and to further verify the validity of the proposed concept. [ABSTRACT FROM AUTHOR]

LTPS TFT full color microLED displays have been developed by incorporating a redundant pixel design to increase the yield of the display, and a covering micro‐reflector array for outcoupling the light emitted from microLEDs has also been proposed. [ABSTRACT FROM AUTHOR]

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A 3.9′ microLED display prototype with LTPS backplanes has been developed by using a newly‐designed current and PWM hybrid driving technology to lower the color shift, resulting in achieving a higher frame rate. A novel approach for a reflector cavity process for improving outcoupling efficiency was also proposed. [ABSTRACT FROM AUTHOR]

Abstract The optical scattering properties of porous polyimide (PI) films were investigated for the light-extraction layer in organic light-emitting diodes (OLEDs). By adjusting mixing ratios of different non-solvents during the immersion precipitation process, the light scattering at the generated porous PIs can be precisely tuned. Analyzed from the final OLED devices based on prepared scattering substrates, we found that the light-output characteristics of fabricated devices are correlated with the optical scattering properties, which depends on both the size of generated pores inside porous PIs and the surface roughness at the air-interface. From the help of Mie scattering and Surface scattering simulations, a systematic approach has been performed to explain the influence of the generated micro-structure on both the optical scattering and OLED-performance. Graphical abstract Image 1 Highlights • Porous light-extraction layers for OLEDs with coated polyimides by immersion precipitation. • Fine control of optical scattering properties through tuning mixing ratios of two non-solvents. • Tuning capabilities of light-outcoupling efficiency and angular emission property in OLEDs. • Systematic approach to correlate optical scattering of porous films with OLED performance. • Analysis of influences of the pore-structures using both Mie scattering and surface scattering. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) currently suffer mostly from only moderate outcoupling efficiencies, calling for many different photonic strategies to increase the share of extracted photons. The quantification of concepts relying on scattering based on periodic or random structures proves complicated and often deserves more attention. To evaluate light extraction methods of OLEDs, we define a procedure leading to a quantifiable extraction efficiency η EE which can be calculated for top- or bottom-emitting OLEDs comprising external as well as internal outcoupling structures. Hence, the extraction efficiency allows to evaluate scattering approaches independently from the employed OLED system. A systematic study of 1D periodically corrugated red top-emitting OLEDs reveals the origin of a moderate enhancement due to an extraction efficiency of η EE  = 14 %. Furthermore, our work provides recommendations how OLEDs with periodic corrugations should be characterized. [ABSTRACT FROM AUTHOR]

Abstract: A key scientific and technological challenge in organic light‐emitting diodes (OLEDs) is enhancing the light outcoupling factor ηout, which is typically <20%. This paper reports experimental and modeling results of a promising approach to strongly increase ηout by fabricating OLEDs on novel flexible nanopatterned substrates that result in a >2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning ηout ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed for blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost‐effectively by direct room‐temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome‐shaped convex nanopatterns with height of ∼280–400 nm and pitch ∼750–800 nm were found to be optimal. Substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs. [ABSTRACT FROM AUTHOR]

High refractive index nanoparticle material was applied as a scattering layer on the inner side of a glass substrate of a bottom emission organic light emitting diode (OLED) device to enhance light extraction and to improve angular color shift. TiO2 and YSZ (Yttria Stabilized Zirconia; Y2O3-ZrO2) were examined as the high refractive index nanoparticles. The nanoparticle material was formed as a scattering layer on a glass substrate by a coating method, which is generally used in the commercial display manufacturing process. Additionally, a planarization layer was coated on the scattering layer with the same method. The implemented nanoparticle material and planarization material endured, without deformation, the subsequent thermal annealing process, which was carried out at temperature ranged to 580 °C. We demonstrated a practical and highly efficient OLED device using the conventional display manufacturing process by implementing the YSZ nanoparticle. We obtained a 38% enhanced luminance of the OLED device and a decreased angular color change compared to a conventional OLED device.

We demonstrate an upscalable approach to increase outcoupling in organic light-emitting diodes (OLEDs) fabricated on flexible substrates. The outcoupling enhancement is enabled by introducing a thin film of microporous polyimide on the backside of silver nanowire (AgNW) electrodes embedded in neat colorless polyimide. This porous polyimide film, prepared by immersion precipitation, utilizes a large index contrast between the polyimide host and randomly distributed air voids, resulting in broadband haze (>75%). In addition, the composite polyimide/AgNW scattering substrate inherits the high thermal (>360 °C), chemical, and mechanical stability of polyimides. The outcoupling efficiency of the composite scattering substrate is studied via optical characterization of the composite substrate and electron microscopy of the scattering film. The flexible scattering substrates compared to glass/indium tin oxide (ITO) allows for a 74% enhancement in external quantum efficiency (EQE) for a phosphorescent green OLED, and 68% EQE enhancement for a phosphorescent white OLED. The outcoupling enhancement remains unharmed after 5000 bending cycles at a 2 mm bending radius. Moreover, the color uniformity over viewing angles is improved, an important feature for lighting applications. [ABSTRACT FROM AUTHOR]

We report on the development and detailed investigation of green phosphorescent organic light-emitting diodes (OLEDs) with porous light-scattering layers prepared by combining a simple coating of polyimide-precursor and the immersion precipitation method. With the proper choice of solvent/non-solvent system in the pore-generation process, an external quantum efficiency ( EQE ) of 30.8% and a power efficiency ( PE ) of 82.2 lm/W can be realized at a luminance of 1000 cd/m 2 . By analyzing the angular characteristics in terms of the luminance- and color-variation of OLEDs fabricated with various porous films, we find that the device performance is closely linked to both the light scattering from the porosity and the ray-path change, which depends on the pore shape. Raytracing optical simulation was also used to confirm that the shape-control of the pores in a porous polymer film modulates the light-outcoupling efficiency in OLEDs. [ABSTRACT FROM AUTHOR]

We review recent progress in controlling the alignment of the transition dipole moment of electroluminescent molecules to maximize the light extraction efficiency in OLEDs. Particular focus devoted to ways of measuring molecular orientation and on linking molecular structure to alignment. [ABSTRACT FROM AUTHOR]

The quantum dot light-emitting diode (QLED) represents one of the strongest display technologies and has unique advantages like a shallow emission spectrum and superior performance based on the cumulative studies of state-of-the-art quantum dot (QD) synthesis and interfacial engineering. However, research on managing the device's light extraction has been lacking compared to the conventional LED field. Moreover, relevant studies on top-emitting QLEDs (TE-QLEDs) have been severely lacking compared to bottom-emitting QLEDs (BE-QLEDs). This paper demonstrates a novel light extraction structure called the randomly disassembled nanostructure (RaDiNa). The RaDiNa is formed by detaching polydimethylsiloxane (PDMS) film from a ZnO nanorod (ZnO NR) layer and laying it on top of the TE-QLED. The RaDiNa-attached TE-QLED shows significantly widened angular-dependent electroluminescence (EL) intensities over the pristine TE-QLED, confirming the effective light extraction capability of the RaDiNa layer. Consequently, the optimized RaDiNa-attached TE-QLED achieves enhanced external quantum efficiency (EQE) over the reference device by 60%. For systematic analyses, current-voltage-luminance (J-V-L) characteristics are investigated using scanning electron microscopy (SEM) and optical simulation based on COMSOL Multiphysics. It is believed that this study's results provide essential information for the commercialization of TE-QLEDs., (© 2023 Wiley-VCH GmbH.)

Enhancement of outcoupling efficiency of OLEDs by using a buckled or wrinkled substrate has been recently reported by several groups, while an optical analysis for understanding the coupling between various modes in OLED devices has not been conducted. For various wrinkle shape, FDTD simulation was conducted to find the external quantum efficiency improved by the coupling into a radiation mode, and the power fraction of various modes existing in the OLED device was examined. Consequently, we found that the coupling between TE mode and surface plasmon mode was critically affecting the fraction of outcoupled mode. For confirming the simulation results with an experiment, the wrinkled OLED device was fabricated by incorporating a novel UV curable liquid prepolymer material. The experimental result corresponded well to the prediction from FDTD analysis. [ABSTRACT FROM PUBLISHER]

This work presents the possibility of the hollow core nanoparticles to improve luminance in an organic light emitting diode device. The finite difference time domain simulation estimates the effect of the hollow core nanoparticles on the external quantum efficiency of the organic light emitting diode device. The efficiency depends on the size and the volume fraction of the hollow core nanoparticles in the polymer layer, together with the refractive index and the thickness of the polymer layer. It is shown that the hollow core nanoparticles dispersed in a polymer layer can enhance the external quantum efficiency by a factor of 2.5. This work also introduces a continuous production method of the hollow core nanoparticles by using the microfluidic self-assembly of amphiphilic polymers and the layer formation dispersed with them for the rigorous light scattering. [ABSTRACT FROM AUTHOR]

Scattering particles find application in organic light emitting diodes (OLEDs) for an enhanced outcoupling of the generated light. This paper presents a computational scheme to exactly model the electromagnetic fields and the power outcoupling efficiency of a typical OLED geometry, comprising a thin film system with spherical scattering particles inside. The model is based on the expansion of the fields in plane and spherical vector wave functions, as well as the scattering matrix formalism for the layer system reflections. In a numerical application example, the effect of 1000 spherical high index scattering particles on the internal outcoupling from a realistic OLED structure is discussed. [ABSTRACT FROM AUTHOR]

The extraction method of surface plasmon polariton (SPP) energy was investigated to assess its ability to improve the outcoupling efficiency of organic light-emitting diodes (OLEDs). A multi-cathode OLED (MC-OLED) structure was used; this structure was composed of a semitransparent cathode (Ag), a high refractive index dielectric layer (WO3), and a reflector (Ag). The dependence of the current efficiency of MC-OLEDs on the thicknesses of the Ag cathode and the WO3dielectric was examined, and optimal thicknesses were identified. Current efficiency can be increased by 20% more than conventional OLEDs by using a 50-nm Ag cathode and a 100-nm WO3dielectric. [ABSTRACT FROM AUTHOR]

We investigated highly efficient organic light emitting diode (OLED) with advanced optical designs of organic layers to convert evanescent mode (internal absorption) into guided light and micro structure to extract the specifically distributed guided light dominated by wide angular substrate mode. White OLED device based on these optical designs realized high efficacy of 133 lm/W and external quantum efficiency of 56 % at 1000 cd/m2. [ABSTRACT FROM AUTHOR]

Highlights: [•] Phosphorescent TrOLEDs have perforated WO3 layer to enhance outcoupling efficiency. [•] Nanostructured TrOLEDs have higher EQE values compared to the conventional TrOLEDs. [•] The values were 28% and 33% higher for bottom and top emission, respectively. [•] The extraction of trapped surface plasmon mode was the main reason for enhancement. [•] The nanostructured TrOLEDs showed optical clarity without haziness. [Copyright &y& Elsevier]

Optimization of angular light distribution in organic layer and light extraction structure based on high refractive index substrate were investigated. Due to advanced optical design for decreasing waveguide and evanescent modes, white OLED device with outstandingly high efficacy of 133 lm/W at 1,000 cd/m2 was realized. [ABSTRACT FROM AUTHOR]

Using a buffer layer under the anode, we studied outcoupling enhancement for organic light-emitting diodes. Monolayers of tungsten oxide and titanium oxide were used as the anode buffer layers. Thin anode buffers such as 25 nm and 50 nm tungsten-oxide layers, and a 15 nm titanium-oxide layer noticeably increased the outcoupling. However, thick buffers decreased the outcoupling. The combined effects of the constructive interference and the creation of additional bound modes explain these behaviors. Therefore, the thickness of the anode buffer layers should be optimized under the upper limit, which creates additional bound modes. [ABSTRACT FROM PUBLISHER]

High-performance two-unit all-phosphorescent white devices on a built-up light extraction substrate that comprised high-index materials were studied. As a result of suitable optical and electrical design, the device showed an extremely high efficacy of 114 lm/W at 1000 cd/m2. The device also showed 102 lm/W with long lifetime (LT70) of over 10,000 h at 3000 cd/m2. Outstanding external quantum efficiency of almost 50% was also achieved in a flat panel with an emissive area of 25 cm2. Color coordinates of the panel met the Energy Star ® criteria of solid-state lighting with CIE (Commission Internationale de l'Éclairage) 1931 ( x, y) = (0.477, 0.423), and the color rendering index was 81. [ABSTRACT FROM AUTHOR]

Outcoupling enhancement methods for organic light-emitting diodes (OLEDs) have been studied using anode and cathode buffers. The outcoupling of OLEDs is enhanced by using thin, high-refractive-index anode buffers, such as 25-nm and 50-nm tungsten-oxide layers and 15-nm titanium-oxide layers. Thick or low-refractiveindex anode buffers reduce outcoupling. OLEDs with 1-nm and 1.5-nm magnesium-fluoride cathode buffers have higher outcoupling than do OLEDs with 0.5-nm cathode buffers. Thin, high-refractive-index anode buffers enhance the extraction of light from the waveguide modes of the anode. As the anode buffer thickness increases, additional waveguide modes form in the anode buffer layer itself and the outcoupling is reduced. Therefore, the thickness of the anode buffer layer should be optimized within a range that does not generate additional bound modes. [ABSTRACT FROM AUTHOR]

We report on a method for fabricating microball lens arrays with high outcoupling efficiency based on the replica molding process, which involves casting liquid polymethylmethacrylate (PMMA) into concave microball lens molds. Concave microball lens molds were fabricated by casting a poly-dimethyl-siloxane (PDMS) mixture onto a monolayer microsphere template, which was prepared by spin-coating an aqueous suspension of polystyrene spheres. Microball lenses were fabricated using microspheres with a diameter of 90 µm. After attaching the microball lens array to organic light-emitting diodes (OLEDs), the luminance was enhanced by approximately 108%. [ABSTRACT FROM AUTHOR]

We present optical simulations of a nanostructured OLED-anode design to enhance the optical outcoupling efficiency. The design allows for the integration of a grating structure with high refractive index contrast into top-emitting OLED microdisplays using CMOS-compatible techniques. [ABSTRACT FROM AUTHOR]

High-performance all-phosphorescent white devices on a light-outcoupling substrate which comprised high-index materials were studied. As a result of suitable optical and electrical design, the device showed an extremely high efficacy of 114 lm/W at 1,000 cd/m2 and 102 lm/W at 3,000 cd/m2. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate a method to increase the efficiency of white organic light emitting diodes (WOLEDs) by a factor of up to 3.7. By fabricating the WOLED on top of a monolayer of SiO2-microspheres we texture the WOLEDs spherically. We attribute the significant increase of the device efficiency to a larger area on the same footprint and to an enhanced outcoupling of waveguide and substrate modes. Measurements reveal that the I–V characteristic of the device as well as the emissive characteristic remains unchanged. [Copyright &y& Elsevier]

A built-up outcoupling substrate with a micro-patterned high refractive index layer was developed in order to obtain both high efficiency and reliability for OLEDs. Light extraction efficiency of this substrate was about 47%, and high efficacy of about 85 lm/W was achieved by the combination with an all phosphorescent white OLED. [ABSTRACT FROM AUTHOR]