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Zhao C, Gong X, Lin X, Zhang C, Wang Y. Regenerated cellulose/polyvinyl alcohol composite films with high transparency and ultrahigh haze for multifunctional light management. Carbohydr Polym 2023; 321:121303. [PMID: 37739533 DOI: 10.1016/j.carbpol.2023.121303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/10/2023] [Accepted: 08/14/2023] [Indexed: 09/24/2023]
Abstract
In this study, cellulose composite films (CCFs) were fabricated through controllable dissolution and regeneration process of cellulose with the addition of polyvinyl alcohol (PVA). The competition of hydrogen bond site between cellulose and PVA led to partial dissolution of cellulose and maintained morphology of micron fibers with width range from 14.55 to 16.16 μm, which served as in-situ visible light scatterers. With this unique micron structure, the obtained CCF exhibited high transparency up to 90.5 % at 550 nm and ultrahigh haze up to 96 %. Interestingly, CCF could be used as hazy and flexible substrate, such as scattering lamp covers for indoor light management, anti-glare screen protectors and anti-reflection layers of solar cell devices. Among them, the efficiency of the solar cell device could be improved by 10.38 % with the help of a low-cost, excellent-performance CCF.
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Affiliation(s)
- Caimei Zhao
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, 483 Wushan Road, Guangzhou 510642, China.
| | - Xinhu Gong
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, 483 Wushan Road, Guangzhou 510642, China.
| | - Xiaotian Lin
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, 483 Wushan Road, Guangzhou 510642, China
| | - Chaoqun Zhang
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, 483 Wushan Road, Guangzhou 510642, China.
| | - Yang Wang
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, 483 Wushan Road, Guangzhou 510642, China.
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Chen E, Zhao M, Chen K, Jin H, Chen X, Sun J, Yan Q, Guo T. Metamaterials for light extraction and shaping of micro-scale light-emitting diodes: from the perspective of one-dimensional and two-dimensional photonic crystals. OPTICS EXPRESS 2023; 31:18210-18226. [PMID: 37381536 DOI: 10.1364/oe.489598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 05/02/2023] [Indexed: 06/30/2023]
Abstract
Metamaterials have attracted broad attention owing to their unique versatile micro- and nano-structures. As a kind of typical metamaterial, photonic crystals (PhCs) are capable of controlling light propagation and constraining spatial light distribution from the chip level. However, introducing metamaterial into micro-scale light-emitting diodes (µLED) still exists many unknowns to explore. This paper, from the perspective of one-dimensional and two-dimensional PhCs, studies the influence of metamaterials on the light extraction and shaping of µLEDs. The µLEDs with six different kinds of PhCs and the sidewall treatment are analyzed based on finite difference time domain (FDTD) method, in which the optimal match between the PhCs type and the sidewall profile is recommended respectively. The simulation results show that the light extraction efficiency (LEE) of the µLEDs with 1D PhCs increases to 85.3% after optimizing the PhCs, and is further improved to reach 99.8% by the sidewall treatment, which is the highest design record so far. It is also found that the 2D air ring PhCs, as a kind of left-handed metamaterials, can highly concentrate the light distribution into 30° with the LEE of 65.4%, without help of any light shaping device. The surprising light extraction and shaping capability of metamaterials provides a new direction and strategy for the future design and application of µLED devices.
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Tang B, Miao J, Liu Y, Wan H, Li N, Zhou S, Gui C. Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall. NANOMATERIALS 2019; 9:nano9030319. [PMID: 30823374 PMCID: PMC6473491 DOI: 10.3390/nano9030319] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/24/2019] [Accepted: 02/26/2019] [Indexed: 11/19/2022]
Abstract
Current solutions for improving the light extraction efficiency of flip-chip light-emitting diodes (LEDs) mainly focus on relieving the total internal reflection at sapphire/air interface, but such methods hardly affect the epilayer mode photons. We demonstrated that the prism-structured sidewall based on tetramethylammonium hydroxide (TMAH) etching is a cost-effective solution for promoting light extraction efficiency of flip-chip mini-LEDs. The anisotropic TMAH etching created hierarchical prism structure on sidewall of mini-LEDs for coupling out photons into air without deteriorating the electrical property. Prism-structured sidewall effectively improved light output power of mini-LEDs by 10.3%, owing to the scattering out of waveguided light trapped in the gallium nitride (GaN) epilayer.
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Affiliation(s)
- Bin Tang
- Key Laboratory of Hydraulic Machinery Transients (Wuhan University), Ministry of Education, Wuhan 430072, China.
| | - Jia Miao
- Key Laboratory of Hydraulic Machinery Transients (Wuhan University), Ministry of Education, Wuhan 430072, China.
| | - Yingce Liu
- Xiamen Changelight Co. Ltd., Xiamen 361000, China.
| | - Hui Wan
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China.
| | - Ning Li
- Key Laboratory of Hydraulic Machinery Transients (Wuhan University), Ministry of Education, Wuhan 430072, China.
| | - Shengjun Zhou
- Key Laboratory of Hydraulic Machinery Transients (Wuhan University), Ministry of Education, Wuhan 430072, China.
- Center for Photonics and Semiconductors, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China.
- State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
| | - Chengqun Gui
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China.
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Li JS, Tang Y, Li ZT, Cao K, Yan CM, Ding XR. Full spectral optical modeling of quantum-dot-converted elements for light-emitting diodes considering reabsorption and reemission effect. NANOTECHNOLOGY 2018; 29:295707. [PMID: 29715198 DOI: 10.1088/1361-6528/aac1b0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantum dots (QDs) have attracted significant attention in light-emitting diode (LED) illumination and display applications, owing to their high quantum yield and unique spectral properties. However, an effective optical model of quantum-dot-converted elements (QDCEs) for (LEDs) that entirely considers the reabsorption and reemission effect is lacking. This suppresses the design of QDCE structures and further investigation of light-extraction/conversion mechanisms in QDCEs. In this paper, we proposed a full spectral optical modeling method for QDCEs packaged in LEDs, entirely considering the reabsorption and reemission effect, and its results are compared with traditional models without reabsorption or reemission. The comparisons indicate that the QDCE absorption loss of QD emission light is a major factor decreasing the radiant efficacy of LEDs, which should be considered when designing QDCE structures. According to the measurements of fabricated LEDs, only calculation results that entirely consider reabsorption and reemission show good agreement with experimental radiant efficacy, spectra, and peak wavelength at the same down-conversion efficiency. Consequently, it is highly expected that QDCE will be modeled considering the reabsorption and reemission events. This study provides a simple and effective modeling method for QDCEs, which shows great potential for their structure designs and fundamental investigations.
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Affiliation(s)
- Jia-Sheng Li
- Engineering Research Center of Green Manufacturing for Energy-Saving and New-Energy Technology, South China University of Technology, Guangdong, 510640, People's Republic of China. Foshan Nationstar Optoelectronics Company Ltd, Foshan 528000, People's Republic of China
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Lee M, Lee H, Song KM, Kim J. Investigation of Forward Tunneling Characteristics of InGaN/GaN Blue Light-Emitting Diodes on Freestanding GaN Detached from a Si Substrate. NANOMATERIALS (BASEL, SWITZERLAND) 2018; 8:E543. [PMID: 30021982 PMCID: PMC6070998 DOI: 10.3390/nano8070543] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 07/10/2018] [Accepted: 07/14/2018] [Indexed: 11/16/2022]
Abstract
We report forward tunneling characteristics of InGaN/GaN blue light emitting diodes (LEDs) on freestanding GaN detached from a Si substrate using temperature-dependent current⁻voltage (T-I-V) measurements. T-I-V analysis revealed that the conduction mechanism of InGaN/GaN LEDs using the homoepitaxial substrate can be distinguished by tunneling, diffusion and recombination current, and series resistance regimes. Their improved crystal quality, inherited from the nature of homoepitaxy, resulted in suppression of forward leakage current. It was also found that the tunneling via heavy holes in InGaN/GaN LEDs using the homoepitaxial substrate can be the main transport mechanism under low forward bias, consequentially leading to the improved forward leakage current characteristics.
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Affiliation(s)
- Moonsang Lee
- Korea Basic Science Institute, 169-148, Gwahak-ro, Yuseong-gu, Daejeon 34133, Korea.
| | - Hyunkyu Lee
- Department of Applied Physics, Hanyang University, Ansan 15588, Korea.
| | - Keun Man Song
- Device Development Department 2, Technology Development Division, 109, Gwanggyo-ro, Yeongtong-gu, Gyeonggi-do, Suwon-Si 16229, Korea.
| | - Jaekyun Kim
- Department of Photonics and Nanoelectronics, Hanyang University, Ansan 15588, Korea.
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Huang YR, Chiu YC, Huang KC, Ting SY, Chiang PJ, Lai CM, Jen CP, Tseng SH, Wang HC. Light extraction efficiency enhancement of flip-chip blue light-emitting diodes by anodic aluminum oxide. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2018; 9:1602-1612. [PMID: 29977694 PMCID: PMC6009532 DOI: 10.3762/bjnano.9.152] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 04/27/2018] [Indexed: 05/29/2023]
Abstract
We produced an anodic aluminum oxide (AAO) structure with periodic nanopores on the surface of flip-chip blue light-emitting diodes (FC-BLEDs). The nanopores had diameters ranging from 73 to 85 nm and were separated by distances ranging from approximately 10 to 15 nm. The light extraction efficiency enhancement of the FC-BLEDs subjected to different durations of the second pore-widening process was approximately 1.6-2.9%. The efficiency enhancement may be attributed to the following mechanism: periodic nanopores on the surface of FC-BLEDs reduce the critical angle of total reflection and effective energy transfer from a light emitter into a surface plasmon mode produced by AAO.
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Affiliation(s)
- Yi-Ru Huang
- Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
| | - Yao-Ching Chiu
- Graduate Institute of Opto-Mechatronics, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan
| | - Kuan-Chieh Huang
- R&D Center, Genesis Photonics Inc., No.5, Dali 3rd Rd., Shanhua Dist., Tainan City 74144, Taiwan
| | - Shao-Ying Ting
- R&D Center, Genesis Photonics Inc., No.5, Dali 3rd Rd., Shanhua Dist., Tainan City 74144, Taiwan
| | - Po-Jui Chiang
- Department of Electronic Engineering, National Kaohsiung University of Applied Sciences, No.415, Jiangong Rd., Sanmin Dist., Kaohsiung City 80778, Taiwan
| | - Chih-Ming Lai
- Department of Electronic Engineering, Ming Chuan University, Taoyuan 333, Taiwan
| | - Chun-Ping Jen
- Department of Mechanical Engineering, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan
| | - Snow H Tseng
- Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
| | - Hsiang-Chen Wang
- Graduate Institute of Opto-Mechatronics, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chia-Yi 62102, Taiwan
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Ke WC, Lee FW, Chiang CY, Liang ZY, Chen WK, Seong TY. InGaN-Based Light-Emitting Diodes Grown on a Micro/Nanoscale Hybrid Patterned Sapphire Substrate. ACS APPLIED MATERIALS & INTERFACES 2016; 8:34520-34529. [PMID: 27998131 DOI: 10.1021/acsami.6b10226] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A hybrid patterned sapphire substrate (hybrid-PSS) was prepared using an anodic aluminum oxide etching mask to transfer nanopatterns onto a conventional patterned sapphire substrate with microscale patterns (bare-PSS). The threading dislocation (TD) suppression of light-emitting diodes (LEDs) grown on a hybrid-PSS (HP-LED) exhibits a smaller reverse leakage current compared with that of LEDs grown on a bare-PSS (BP-LED). The strain-free GaN buffer layer and fully strained InGaN active layer were evidenced by cross-sectional Raman spectra and reciprocal space mapping of the X-ray diffraction intensity for both samples. The calculated piezoelectric fields for both samples are close, implying that the quantum-confined Stark effect was not a dominant mechanism influencing the electroluminescence (EL) peak wavelength under a high injection current. The bandgap shrinkage effect of the InGaN well layer was considered to explain the large red-shifted EL peak wavelength under high injection currents. The estimated LED chip temperatures rise from room temperature to 150 °C and 75 °C for BP-LED and HP-LED, respectively, at a 600-mA injection current. This smaller temperature rise of the LED chip is attributed to the increased contact area between the sapphire and the LED structural layer because of the embedded nanopattern. Although the chip generates more heat at high injection currents, the accumulated heat can be removed to outside the chip effectively. The high diffuse reflection (DR) rate of hybrid-PSS increases the escape probability of photons, resulting in an increase in the viewing angle of the LEDs from 130° to 145°. The efficiency droop was reduced from 46% to 35%, effects which can be attributed to the elimination of TDs and strain relaxation by embedded nanopatterns. In addition, the light output power of HP-LED at 360-mA injection currents exhibits a ∼ 22.3% enhancement, demonstrating that hybrid-PSSs are beneficial to apply in high-power LEDs.
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Affiliation(s)
- Wen-Cheng Ke
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan
| | - Fang-Wei Lee
- Department of Electrophysics, National Chiao-Tung University , HsinChu 300, Taiwan
| | - Chih-Yung Chiang
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan
| | - Zhong-Yi Liang
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan
| | - Wei-Kuo Chen
- Department of Electrophysics, National Chiao-Tung University , HsinChu 300, Taiwan
| | - Tae-Yeon Seong
- Department of Materials Science and Engineering, Korea University , Seoul 02841, Korea
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