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AlGaN deep-ultraviolet light-emitting diodes grown on SiC substrates
摘要： The disinfection industry would greatly benefit from efficient, robust, high-power deep-ultraviolet light-emitting diodes (UV-C LEDs). However, the performance of UV-C AlGaN LEDs is limited by poor light-extraction efficiency (LEE) and the presence of a large density of threading dislocations. We demonstrate high power AlGaN LEDs grown on SiC with high LEE and low threading dislocation density. We employ a crack-free AlN buffer layer with low threading dislocation density and a technique to fabricate thin-film UV LEDs by removing the SiC substrate, with a highly selective SF6 etch. The LEDs (278 nm) have a turn-on voltage of 4.3 V and a CW power of 8 mW (82 mW/mm2) and external quantum efficiency (EQE) of 1.8% at 95 mA. KOH submicron roughening of AlN surface (nitrogen-polar) and improved p-contact reflectivity are found to be effective in improving the LEE of UV light. We estimate the improved LEE by semi-empirical calculations to be 33% (without encapsulation). This work establishes UV LEDs grown on SiC substrates as a viable architecture to large-area, high-brightness, and high power UV LEDs.
关键词： AlGaN LEDs,UV-C LEDs,light extraction efficiency,disinfection technology,AlN,external quantum efficiency,SiC,substrate removal
更新于2025-09-19 17:13:59
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Enhancement of Light Extraction from Organic Light-Emitting Diodes by SiO <sub/>2</sub> Nanoparticle-Embedded Phase Separated PAA/PI Polymer Blends
摘要： Using the phase separation of a binary immiscible polymer blend of poly(amic acid) and polyimide in combination with SiO2 nanoparticles, we have designed random nanopore and nanopillar patterns by a simple spin-coating technique. The spontaneously formed pattern structure was investigated by an atomic force microscope technique, which enhanced the external quantum efficiency of conventional green OLEDs up to a highest factor of 1.42. This enhancement is mainly attributed to the reduction of the total internal reflection at the interface of glass and air by the polymer hybrid layer on the backside of OLED devices. This work provides a new and practical approach to the development of efficient external outcoupling structures for OLEDs.
关键词： Poly(amic acid)/Polyimide (PAA/PI),phase separation,light extraction,nanoparticles,nanopores and nanopillars
更新于2025-09-19 17:13:59
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P‐9.1: QD based color converter with DBR Structure and its application on Micro‐LED
摘要： An enhancement of light extraction efficiency of quantum dots (QD) (LEDs) with Bi-functional TiO2/Al2O3 distributed Bragg reflector (DBR) nanolaminate structure grown by atomic layer deposition (ALD) has been demonstrated. The DBRs were simulated and optimized with TFCalc, and they exhibited excellent and tunable optical properties, as well as reliable moisture barrier performance. These DBRs were integrated in the QD-LED, enabling an obvious increase in red emission and a strong decrease in blue light transmittance, which can achieve color conversion greatly. Furthermore, these DBRs can prolong the lifetime of QDs evidently by isolating the QDs from the moisture vapor. These results highlight the potential application of DBRs in the QLEDs and QD-LEDs.
关键词： atomic layer deposition (ALD),simulation,distributed Bragg reflector (DBR),water vapor transmission rates (WVTR),light extraction efficiency
更新于2025-09-19 17:13:59
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Improving the performance of light-emitting diodes via plasmonic-based strategies
摘要： Light-emitting diodes (LEDs), featuring long lifetime, small size, and low energy consumption, are increasingly popular for displays and general light sources. In the past decades, new light-emitting materials and novel device configurations are being continuously investigated to obtain highly efficient LEDs. Nevertheless, the unsatisfying external quantum efficiency severely limits their commercial implementation. Among all the approaches to boost the efficiency of LEDs, the incorporation of plasmonic structures exhibits great potential in increasing the spontaneous emission rates of emitters and improving the light extraction efficiency. In this Perspective, the methods to deal with challenges in quantum-well-based LEDs and organic LEDs by employing plasmonic materials are described, the mechanisms of plasmonic-based strategies to improve the light generation and extraction efficiency are discussed, and the plasmonic control over directional emission of phosphors is introduced as well. Moreover, important issues pertaining to the design, fabrication, and manipulation of plasmonic structures in LEDs to optimize the device performance, as well as the selection roles in finding appropriate plasmonic materials and structures for desired LED devices, are explained. This perspective lists the challenges and opportunities of plasmonic LEDs, with the aim of providing some insights into the future trends of plasmonic LEDs.
关键词： spontaneous emission rates,light-emitting diodes,light extraction efficiency,external quantum efficiency,plasmonic structures
更新于2025-09-16 10:30:52
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Effect of a thin Au and ZnO layer on optical properties of 1D PhC structures patterned in LED surface
摘要： 1D patterns with different periods were fabricated by Electron Beam Direct Write (EBDW) lithography with the aim to improve the Light Emitting Diode (LED) efficiency, i.e. the light out coupling. Three sets of 1D PhC LED samples with bare PhC, thin Au, and ZnO layers were prepared. The highest Light Extraction Enhancement (LEE) was achieved for 600 nm Photonic Crystals (PhC) period in the case of bare and Au deposited PhC, and for 500 nm PhC period in the case of ZnO deposited PhC, respectively. LEE was studied by measuring L-I characteristics of untreated reference LEDs compared to patterned LEDs.
关键词： LED efficiency,Light extraction enhancement,Photonic crystals,1D structures,EBDW lithography,HSQ XR 1541 resist
更新于2025-09-16 10:30:52
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[IEEE 2019 41st Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) - Berlin, Germany (2019.7.23-2019.7.27)] 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - A wearable phototherapy device utilizing micro-LEDs
摘要： A conformable device for wearable phototherapy applications is presented. The device consists of a 1mm thick elastomeric membrane edge-lit by specially fabricated micro-sized LEDs. Nanoparticle based scattering films are utilized to extract light and a uniform emission of 15μW/cm2 is reported over an area of 2cm2.
关键词： micro-LEDs,elastomeric membrane,light extraction,wearable phototherapy,uniform emission
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Seoul, Korea (South) (2019.1.27-2019.1.31)] 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Flexible $\mu\text{LED}$-Based Optogenetic Tool with Integrated $\mu$-Lens Array and Conical Concentrators Providing Light Extraction Improvements above 80%
摘要： This paper reports on the fabrication and characterization of spherical micro-lenses (μ-lenses) made from polydi-methylsiloxane (PDMS) and their integration into optogenetic implants based on micro light-emitting diodes (μLEDs). The μ-lenses are fabricated using a reusable silicon mold realized by wet chemical HNA (hydrofluoric, nitric and acetic acid) etching. It applies a masking layer with openings as small as 5 μm and was optimized for hemispherical μ-lens cavities of low surface roughness (Ra < 45 nm). The μ-lenses with diameters down to 10 μm are realized by PDMS molding using a polymeric release layer (PRL) improving the μ-lens release and enabling Ra values below 5 nm. Linear μ-lens arrays are transferred onto the emission side of μLEDs comprising integrated conical concentrators (CCs). The PDMS-filled CCs improve the μ-lens emission behavior by light reflection at the interface between the polymeric probe substrate and PDMS, without increasing the overall probe dimensions. Using μLEDs with integrated μ-lens arrays in combination with CCs, the overall light extraction of the optical implants is increased by 115 % and 83 % in air and water, with the peak intensity raised by 145 % and 95 %, respectively.
关键词： optogenetic implants,conical concentrators,PDMS,light extraction,μ-lenses,μLEDs
更新于2025-09-12 10:27:22
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Effect of photonic crystals on the light extraction of GaN-based LED for different polarization modes of spontaneous radiation
摘要： The light extraction efficiency (LEE) of different polarization modes have been simulated by FDTD solutions for three photonic crystal (PhC) structures, which are spherical-PhC LED, cylindrical-PhC LED and compound-PhC LED. The TE-and TM-mode LEE are simulated seperately. It shows that the discontinuity of the structure from the propagation direction will cause decrease of TE-mode and TM-mode LEE. TE and TM mode are enhanced by 60% and 40% in cylindrical-PhC LED, in which the single nanorod act as light waveguide. Finally, a multi-layer-compound-PhC-LED is proposed. Results show that the TM-mode LEE based on this structure is increased by 1.45 times at a wavelength of 532 nm, and the TM-mode illuminous intensity will be larger than that of TE mode, and then polarization inversion occurs.
关键词： GaN-based LED,Polarization,Photonic crystals,Light extraction efficiency
更新于2025-09-12 10:27:22
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7.2: <i>Invited Paper:</i> High Efficiency Internal Extraction Substrate for OLED Lighting
摘要： FOL’s OCEANCLEAR series high-efficiency IES (internal extraction structure) substrates have actually been applied to Gen-II line for mass production. White OLED panels made on basis of the IES substrates show a power efficacy of around 95lm/W at 1000cd/m2. A candlelight-style desk lamp used IES panel shows a color temperature of around 1700k, a power efficacy of 60lm/W at 1000cd/m2. Mass production of IES substrates where achieved by two key technologies: one-layer coating method and heat-resisting carrier resin formation.
关键词： white OLED,internal extraction,light extraction,candle light OLED,extraction substrate,lighting,OLED
更新于2025-09-11 14:15:04
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Highly-Conductive, Transparent Ga-Doped ZnO Nanoneedles for Improving the Efficiencies of GaN Light-Emitting Diode and Si Solar Cell
摘要： The growths of transparent, highly-conductive Ga-doped ZnO (GaZnO) nanoneedles (NNs) on the tops of GaN-based light-emitting diodes (LEDs) and Si solar cells for enhancing light extraction and reducing surface reflection, respectively, and hence increasing their efficiencies are demonstrated. The GaZnO NNs are grown based on the vapor-liquid-solid process by using surface Ag nanoparticles (NPs) as growth catalyst. In the application to LED, the residual Ag NPs can induce the surface plasmon (SP) coupling effect for increasing the LED emission efficiency. By combining the SP coupling effect, the light extraction effects of the GaZnO NNs and simultaneously deposited GaZnO thin film, and the current spreading effect of the thin film, the LED output intensity can be increased by 100%. In the solar cell application, the SP resonance of the residual Ag NPs can also enhance sunlight harvest and hence the energy conversion efficiency. By combining the effects of the residual Ag NPs, the GaZnO thin film, and the GaZnO NNs, the energy conversion efficiency of a Si solar cell can increase from 9.65 to 12.30%, corresponding to a relative enhancement of 27.5%.
关键词： Ga-doped ZnO,light extraction,light-emitting diodes,solar cells,surface plasmon,anti-reflection,nanoneedles
更新于2025-09-11 14:15:04