Ni–Cu Nanoparticles-Embedded Ag-Based Reflector for High-Efficiency Light-Emitting Diodes

2020 ◽  
Vol 20 (11) ◽  
pp. 6732-6737
Author(s):  
Eun-Kyung Chu ◽  
Kab Ha ◽  
Beom-Rae Noh ◽  
Young-Ju Kwon ◽  
Semi Oh ◽  
...  
Keyword(s):  
Flip Chip ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Forward Bias ◽  
Light Output ◽  
Single Layer ◽  
Cu Nanoparticles ◽  
Light Emitting ◽  
Forward Bias Voltage ◽  
Ag Reflector

We investigated the use of a silver reflector embedded with Ni–Cu nanoparticles to achieve low resistance and high reflectivity in GaN-based flip-chip light-emitting diodes. Compared to a single layer of Ag, the NC-NPs/Ag reflector exhibits a higher light reflectance of ~90% at a wavelength of 450 nm, a lower contact resistance of 4.75 × 10−5 II cm2, and improved thermal stability after annealing at 400°C. The NC-NPs formed after the annealing process prevents agglomeration of the Ag layer, while also reducing the Schottky barrier height between the p-GaN layer and metal reflector. The LED fabricated with a NC-NPs/Ag reflector exhibited a forward-bias voltage of 3.13 V and an improvement in light output power of 36.6% (at 20 mA), when compared with the LED composed of a Ag SL. This result indicates that the NC-NPs/Ag reflector is a promising p-type reflector for high-intensity light-emitting diodes.

scholarly journals Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 650 ◽  
Author(s):  
Shengjun Zhou ◽  
Haohao Xu ◽  
Mengling Liu ◽  
Xingtong Liu ◽  
Jie Zhao ◽  
...  
Keyword(s):  
Flip Chip ◽  
Heat Dissipation ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Incident Angle ◽  
Light Output ◽  
Bragg Reflector ◽  
Distributed Bragg Reflector ◽  
Light Emitting ◽  
Via Hole

We demonstrated two types of GaN-based flip-chip light-emitting diodes (FCLEDs) with distributed Bragg reflector (DBR) and without DBR to investigate the effect of dielectric TiO2/SiO2 DBR on optical and electrical characteristics of FCLEDs. The reflector consisting of two single TiO2/SiO2 DBR stacks optimized for different central wavelengths demonstrates a broader reflectance bandwidth and a less dependence of reflectance on the incident angle of light. As a result, the light output power (LOP) of FCLED with DBR shows 25.3% higher than that of FCLED without DBR at 150 mA. However, due to the better heat dissipation of FCLED without DBR, it was found that the light output saturation current shifted from 268 A/cm2 for FCLED with DBR to 296 A/cm2 for FCLED without DBR. We found that the use of via-hole-based n-type contacts can spread injection current uniformly over the entire active emitting region. Our study paves the way for application of DBR and via-hole-based n-type contact in high-efficiency FCLEDs.

GaN-based Light Emitting Diode with Transparent Nanoparticles-Embedded p-Ohmic Electrodes

2005 ◽  
Vol 892 ◽  
Author(s):  
June-O Song ◽  
Hun Kang ◽  
David Nicol ◽  
Ian T Ferguson ◽  
Hyun-Gi Hong ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Indium Tin Oxide ◽  
Flip Chip ◽  
New Technologies ◽  
Light Emitting Diode ◽  
Forward Bias ◽  
Light Output ◽  
Contact Layer ◽  
Light Emitting ◽  
Forward Bias Voltage

AbstractOptoelectronics related to GaN-based semiconductors (i.e., InGaN, GaN, and AlGaN) are new technologies that have the potential to far exceed the energy efficiencies of incandescent and fluorescent lighting sources. Among the GaN-based optoelectronic devices like light emitting diode (LED) and laser diode (LD), the GaN-based LEDs are of interest for the next generation illumination because of the representative characteristics such as small, highly radiant, reliably long, and fast responding, compared with the existing general lighting systems.Achievement of high luminous intensity by flip-chip LED (FCLED) with Ag-metallic reflector or using top emitting LED (TELED) with highly transparent ITO contact is required to improve the external quantum efficiency (EQE) and light output of GaN-based LEDs. However, since the work function of Ag and ITO is lower than 5.0 eV, it is difficult to produce low-resistance p-ohmic electrode with Ag-metallic reflector or ITO only.In this study, in order to develop new ohmic contact materials having low contact resistance and high transmittance, transparent nanoparticles-embedded p-ohmic electrode, Mg-doped indium oxide (MIO) (3 nm)/indium tin oxide (ITO) (400 nm) ohmic contact for high brightness TELEDs for solid-state lighting, was suggested. The MIO/ITO contact become ohmic with specific contact resistances of 2.64 × 10-3 Ωcm2 and give transmittance higher than 94.6 % at a wavelength of 450 nm when annealed at 630 °C for 1 min in air. GaN-based LEDs fabricated with the annealed MIO/ITO p-contact layer give a forward-bias voltage of about 3.38 V at injection current of 20 mA. It is further shown that the output power of the LEDs with the MIO/ITO contact is enhanced by about 1.86 times at 20 mA as compared with that of LEDs with the conventional Ni/Au contact.

scholarly journals High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

Nanomaterials ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 1178 ◽  
Author(s):  
Qiang Zhao ◽  
Jiahao Miao ◽  
Shengjun Zhou ◽  
Chengqun Gui ◽  
Bin Tang ◽  
...  
Keyword(s):  
High Power ◽  
Silicon Substrate ◽  
Flip Chip ◽  
Heat Dissipation ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Current Spreading ◽  
Light Emitting ◽  
Fabry Perot ◽  
Lift Off

We demonstrate high-power GaN-based vertical light-emitting diodes (LEDs) (VLEDs) on a 4-inch silicon substrate and flip-chip LEDs on a sapphire substrate. The GaN-based VLEDs were transferred onto the silicon substrate by using the Au–In eutectic bonding technique in combination with the laser lift-off (LLO) process. The silicon substrate with high thermal conductivity can provide a satisfactory path for heat dissipation of VLEDs. The nitrogen polar n-GaN surface was textured by KOH solution, which not only improved light extract efficiency (LEE) but also broke down Fabry–Pérot interference in VLEDs. As a result, a near Lambertian emission pattern was obtained in a VLED. To improve current spreading, the ring-shaped n-electrode was uniformly distributed over the entire VLED. Our combined numerical and experimental results revealed that the VLED exhibited superior heat dissipation and current spreading performance over a flip-chip LED (FCLED). As a result, under 350 mA injection current, the forward voltage of the VLED was 0.36 V lower than that of the FCLED, while the light output power (LOP) of the VLED was 3.7% higher than that of the FCLED. The LOP of the FCLED saturated at 1280 mA, but the light output saturation did not appear in the VLED.

scholarly journals Highly Efficient Single-Layer Phosphorescent Organic Light-Emitting Diodes Based on Co-Host Structure

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2029
Author(s):  
Tianyu Zhang ◽  
Asu Li ◽  
Ren Sheng ◽  
Mingyang Sun ◽  
Ping Chen
Keyword(s):  
High Efficiency ◽  
Light Emitting Diodes ◽  
Single Layer ◽  
Charge Carriers ◽  
Organic Light Emitting Diodes ◽  
Superior Performance ◽  
Light Emitting ◽  
Organic Light ◽  
Exciton Recombination ◽  
Host Structure

High-efficiency single-layer organic light-emitting diodes (OLEDs) based on a simple structure doped with iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C2′) acetylacetonate (PO-01) as emission dyes are realized, achieving maximum current efficiency (CE) and power efficiency (PE) of 37.1 cd A−1 and 33.3 lm W−1 as well as low turn-on voltage of 3.31 V. Such superior performance is mainly attributed to the employment of a uniform co-host structure and assisted charge transport property of phosphors dyes, which were in favor of the balance of charge carrier injection and transport in the single emitting layer (EML). Moreover, systematic researches on the position of exciton recombination region and the dopant effect on charge carriers were subsequently performed to better understand the operational mechanism. It could be experimentally found that the orange emitting dopants promoted the acceleration of the charge carriers transport and raised the exciton recombination efficiency, eventually leading to an excellent performance of single-layer OLEDs.

scholarly journals Performance Improvement of GaN-Based Flip-Chip White Light-Emitting Diodes with Diffused Nanorod Reflector and with ZnO Nanorod Antireflection Layer

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Hsin-Ying Lee ◽  
Yu-Chang Lin ◽  
Yu-Ting Su ◽  
Chia-Hsin Chao ◽  
Véronique Bardinal
Keyword(s):  
Blue Light ◽  
White Light ◽  
Flip Chip ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Nanorod Array ◽  
Zno Nanorod ◽  
Light Emitting ◽  
Zno Nanorod Array ◽  
White Light Emitting Diodes

The GaN-based flip-chip white light-emitting diodes (FCWLEDs) with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. The light output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layer were improved from 21.15 mW to 23.90 mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively.

High efficiency red phosphorescent organic light-emitting diodes with single layer structure

2010 ◽  
Vol 11 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Woo Sik Jeon ◽  
Tae Jin Park ◽  
Kyeong Heon Kim ◽  
Ramchandra Pode ◽  
Jin Jang ◽  
...  
Keyword(s):  
High Efficiency ◽  
Light Emitting Diodes ◽  
Layer Structure ◽  
Single Layer ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light

scholarly journals Size-Dependent Quantum Efficiency of Flip-Chip Light-Emitting Diodes at High Current Injection Conditions

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 88
Author(s):  
Xingfei Zhang ◽  
Yan Li ◽  
Zhicong Li ◽  
Zhenlin Miao ◽  
Meng Liang ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Current Density ◽  
Flip Chip ◽  
Light Emitting Diodes ◽  
Light Output ◽  
Current Injection ◽  
High Current ◽  
High Quantum Efficiency ◽  
Light Emitting ◽  
Size Dependent

Versatile applications call for InGaN-based light-emitting diodes (LEDs) to operate at ultra-high current densities with high quantum efficiency. In this work, we investigated the size-dependent effects of the electrical and optical performance of LEDs as increasing the current density up to 100 A/cm2, which demonstrated that mini-strip flip-chip LEDs were superior option to achieve better performance. In detail, at a current density of 100 A/cm2, the light output power density of these mini-strip LEDs was improved by about 6.1 W/cm2, leading to an improvement in the wall-plug efficiency by 4.23%, while the operating temperature was reduced by 11.3 °C, as compared with the large-sized LEDs. This could be attributed to the increase in the sidewall light extraction, alleviated current crowding effect, and improved heat dissipation. This work suggests an array of mini-strip LEDs would provide an option in achieving higher luminescent efficiency at ultrahigh current injection conditions for various applications.

Improvement of Luminous Efficiency in White Light Emitting Diodes by Reducing a Forward-bias Voltage

2007 ◽  
Vol 46 (No. 40) ◽  
pp. L963-L965 ◽  
Author(s):  
Yukio Narukawa ◽  
Masahiko Sano ◽  
Masatsugu Ichikawa ◽  
Shunsuke Minato ◽  
Takahiko Sakamoto ◽  
...  
Keyword(s):  
Bias Voltage ◽  
White Light ◽  
Light Emitting Diodes ◽  
Forward Bias ◽  
Luminous Efficiency ◽  
Light Emitting ◽  
Forward Bias Voltage ◽  
White Light Emitting Diodes
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