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This study investigates the application of scattering structures to the metal layer in a DMD (Dielectric/Metal/Dielectric) configuration through plasma treatment. The purpose is to enhance the light extraction efficiency of organic light-emitting diodes (OLEDs). Different plasma conditions were explored to create scattering structures on the metal layer. The fabricated devices were characterized for their electrical and optical properties. The results demonstrate that the introduction of scattering structures through plasma treatment effectively improves the light extraction efficiency of OLEDs. Specifically, using O2-plasma treatment on the metal layer resulted in significant enhancements in the total transmittance, haze, and figure of merit. These findings suggest that incorporating scattering structures within the DMD configuration can effectively promote light extraction in OLEDs, leading to enhanced overall performance and light efficiency.

Light-emitting diodes (LEDs) based on Gallium Nitride (GaN) have been revolutionizing various applications in lighting, displays, biotechnology, and other fields. However, their energy efficiency is still below expectations in many cases. An unprecedented diversity of theoretical models has been developed for efficiency analysis and GaN-LED design optimization, including carrier transport models, quantum well recombination models, and light extraction models. This invited review paper provides an overview of the modeling landscape and pays special attention to the influence of III-nitride material properties. It thereby identifies some key challenges and directions for future improvements.

This study proposes a novel hybrid substrate that integrates a microlens array (MLA) with a polymer dispersed liquid crystal (PDLC) to enhance external light extraction efficiency in flexible organic light emitting diodes (OLEDs). The proposed MLA imprinted PDLC (MIP) substrate significantly improves light extraction by synergistically combining the strong volumetric scattering of the PDLC with the interfacial refraction of the MLA. Simultaneously, the polymer matrix provides excellent mechanical flexibility, making the substrate well suited for flexible OLED applications. The validity of the proposed structure was verified through Monte Carlo ray-tracing simulations. When applied to flexible OLEDs, the MIP substrate exhibits a high haze of 98.5% and achieves a 21% enhancement in external quantum efficiency (EQE) compared with a reference device. The MIP is fabricated through a simple room temperature solution process involving only spin coating and UV curing. This facile method provides excellent scalability for large area applications, including roll-to-roll and printing processes. Thus, the proposed MIP platform offers a practical and effective approach for advancing next generation flexible optoelectronics.

Top-emitting microcavity OLEDs (TEOLEDs) exhibit excellent color purity but suffer from severe angular color shifts. To overcome this, we introduce a nanotextured light modulation strategy using a nanoporous film (NPF) and an index-matched optically clear resin (OCR) for encapsulation. The nanotextured NPF enhances light outcoupling while suppressing cavity-induced angular dependence. As a result, the external quantum efficiency (EQE) is enhanced by 370% (from 8.5 to 31.6%), and angular color shift (Δu′v′) is reduced by 65.2% (from 0.046 to 0.016). By introducing a nanostructure-based light modulation technology, we have achieved a breakthrough in microcavity OLED performance, simultaneously improving both outcoupling and angular stability. Applied to flexible TEOLEDs, the device exhibits stable optical and mechanical performance under bending. This scalable and effective light modulation design enables highly efficient and color-stable flexible OLED displays for next-generation wearable applications.

Micro-LEDs (µLEDs) are poised to transform near-eye AR/VR, display, and optical communication technologies, but they are currently hindered by low light extraction efficiency and non-directional emission. Our study introduces an innovative approach using a descending index multilayer anti-reflection coating combined with a horn collimator structure atop the µLED pixel. This design leverages the propagation of light outside the critical angle to enhance both the directionality and extraction efficiency of emitted light. By implementing either discrete or continuous refractive index gradients within the horn, we achieve a tenfold increase in light extraction within a cone, with an overall light extraction efficiency reaching approximately 80%, where 31% of the power is concentrated within this narrow cone. The enhancement is furthermore maintained across a broad range of Quantum well position variations. This performance surpasses that of an optimized SiO2 half-ellipsoidal lens, which diameter and height is 24X and 26X larger than the pixel width respectively, while our design only slightly increases the device height and expands the final light escape surface to 3 times and roughly 4 times the pixel width respectively. Such efficiency, directionality enhancement, and compactness make this solution particularly suitable for high-resolution, densely packed µLED arrays, promising advancements in high-performance, miniaturized display systems.

The external-quantum efficiency (EQE) of AlGaN-based ultraviolet-B light-emitting diodes (UVB LEDs) has achieved a world record value of 9.6% on wafers but suffers from a low light extraction efficiency (LEE) of < 15%, notably lower than that of the LEE of InGaN blue LEDs (> 89%). This study employed the finite-difference time-domain (FDTD) method to explore how micro-patterned c-plane Sapphire substrates (microPSS) or nano-patterned c-plane Sapphire substrates (nanoPSSs) and reflecting photonic crystals (R-PhCs) influence light scattering in flip-chipped AlGaN-based UVB LEDs, with or without an Al-side reflector. First, various microPSS and nanoPSS shapes (Pillar-like and Hole-like) were analysed by the FDTD to optimise the pitch (a), diameter (d), height (h), and diffraction order (m) under Bragg’s condition. The nanoPSS were found most effective for UVB LEDs at an emission peak of 304 nm with cylindrical Hole-like nanoPSS (m = 10, d = 596 nm, a = 746 nm, h = 500 nm, R/a = 0.38), (R is the radius of the holes of the nanoPSS or PhC) improving LEE enhancement to the maximum possible value of approximately 18%. Next, an Al-side reflector was introduced to evaluate the combined impact of optimised nanoPSS and R-PhC (Hole-like) on theoretical light extraction. Parameters (m = 3; h = 150 nm; R/a = 0.40) applied in p-GaN or p-AlGaN contact layers boosted light extraction to approximately 148% or 150% (with an Al-side reflector) and approximately 120% (without an Al-side reflector), marking significant theoretical and experimental advancements in AlGaN UVB LED efficiency.

Micro-LED display technology has been considered a promising candidate for near-eye display applications owing to its superior performance, such as having high brightness, high resolution, and high contrast. However, the realization of polarized and high-efficiency light extraction from Micro-LED arrays is still a significant problem to be addressed. Recently, by exploiting the capability of metasurfaces in wavefront modulation, researchers have achieved many excellent results by integrating metasurface structures with Micro-LEDs, including improving the light extraction efficiency, controlling the emission angle to achieve directional emission, and obtaining polarized Micro-LEDs. In this paper, recent progressions on Micro-LEDs integrated with metasurface structures are reviewed in the above three aspects, and the similar applications of metasurface structures in organic LEDs, quantum dot LEDs, and perovskite LEDs are also summarized.

Organic light emitting diode (OLED) technology continues to make strides, particularly in display technology, with costs decreasing and consumer demand growing. Advances are also seen in OLED solid state lighting (SSL) though broad utilization of this technology is lagging. This situation has prompted extensive R&D to achieve high-efficiency SSL devices at cost-effective fabrication. Here we review the advances and challenges in enhancing forward light outcoupling from OLEDs. Light outcoupling from conventional bottom-emitting OLEDs (through a transparent anode) is typically ∼20%, largely due to external losses, i.e., substrate waveguide modes, internal waveguide modes between the metal cathode and the anode/substrate interface, and surface plasmon-polariton modes at the metal cathode/organic interface. We address these major photon loss paths, presenting various extraction approaches. Some approaches are devoid of light extraction structures; they include replacing the commonly used ITO anode, manipulating the refractive index of the substrate and/or organic layers, and evaluating emitters with preferential horizontal transition dipoles. Other approaches include the use of enhancing structures such as microlens arrays, scattering layers and patterned substrates, as well as substrates with various buried structures that are planarized by high index layers. A maximal external quantum efficiency as high as 78% was reported for white planarized OLEDs with a hemispherical lens to extract the substrate mode. Light outcoupling from OLEDs on flexible substrates is also addressed, as the latter become of increasing interest in foldable displays and decorative lighting, with plastic substrates also being evaluated for biomedical, wearable, and automotive applications.

We report a feasible method to realize tunable surface plasmon-polariton (SPP) resonance in organic light-emitting devices (OLEDs) by employing corrugated Ag-Al alloy electrodes.The excited SPP resonance induced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes.With an appropriate composition ratio of the corrugated alloy electrode,the photons trapped in SPP modes are recovered and extracted ef-fectively.The 25％ increasement in luminance and 21％ enhancement in current efficiency have been achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.