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Maity A, Biswas V, Vijaya R. Control of visible-range transmission and reflection haze by varying pattern size, shape and depth in flexible metasurfaces. FRONTIERS OF OPTOELECTRONICS 2024; 17:25. [PMID: 39078525 PMCID: PMC11289189 DOI: 10.1007/s12200-024-00125-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Accepted: 06/21/2024] [Indexed: 07/31/2024]
Abstract
Cost-effective soft imprint lithography technique is used to prepare flexible thin polymeric surfaces containing a periodic arrangement of nanodimples and nanobumps of sub-micron size. Using a single master mold of self-assembled colloidal crystal, metasurfaces with different depths and heights of patterns with a fixed pitch are possible, which makes the process inexpensive and simple. These metasurfaces are studied for their diffuse and total transmission and reflection spectra in the visible range. The transmission haze and reflection haze are calculated from the measurements. The surface containing nanobumps of lesser pattern height result in higher values of reflection and transmission haze than from surfaces containing nanodimples of much higher depth for the same pitch. The haze is more dependent on the pattern depth or height and less dependent on the pitch of the pattern. Far-field transmission profiles measured in the same wavelength range from the patterned surfaces show that the scattering increases with the increase of the ratio of pattern depth/height to pitch, similar to the haze measurements conducted with a closed integrating sphere. These profiles show that the angular spread of scattered light in transmission is within 10°, explaining the reason for the relatively low transmission haze in all the patterned surfaces. Simulation results confirm that the nanobump pattern gives higher transmission haze compared to nanodimple pattern. By controlling the ratio of pattern depth/height to pitch of the features on these surfaces, both an increase in optical haze and a balance between total reflection intensity and total transmission intensity can be achieved.
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Affiliation(s)
- Avijit Maity
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Vaswati Biswas
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - R Vijaya
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
- Centre for Lasers and Photonics, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
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Kumar S, Seo Y. Flexible Transparent Conductive Electrodes: Unveiling Growth Mechanisms, Material Dimensions, Fabrication Methods, and Design Strategies. SMALL METHODS 2023:e2300908. [PMID: 37821417 DOI: 10.1002/smtd.202300908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/09/2023] [Indexed: 10/13/2023]
Abstract
Flexible transparent conductive electrodes (FTCEs) constitute an indispensable component in state-of-the-art electronic devices, such as wearable flexible sensors, flexible displays, artificial skin, and biomedical devices, etc. This review paper offers a comprehensive overview of the fabrication techniques, growth modes, material dimensions, design, and their impacts on FTCEs fabrication. The growth modes, such as the "Stranski-Krastanov growth," "Frank-van der Merwe growth," and "Volmer-Weber growth" modes provide flexibility in fabricating FTCEs. Application of different materials including 0D, 1D, 2D, polymer composites, conductive oxides, and hybrid materials in FTCE fabrication, emphasizing their suitability in flexible devices are discussed. This review also delves into the design strategies of FTCEs, including microgrids, nanotroughs, nanomesh, nanowires network, and "kirigami"-inspired patterns, etc. The pros and cons associated with these materials and designs are also addressed appropriately. Considerations such as trade-offs between electrical conductivity and optical transparency or "figure of merit (FoM)," "strain engineering," "work function," and "haze" are also discussed briefly. Finally, this review outlines the challenges and opportunities in the current and future development of FTCEs for flexible electronics, including the improved trade-offs between optoelectronic parameters, novel materials development, mechanical stability, reproducibility, scalability, and durability enhancement, safety, biocompatibility, etc.
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Affiliation(s)
- Sunil Kumar
- Department of Nanotechnology and Advanced Materials Engineering and HMC, Sejong University, Seoul, 05006, South Korea
| | - Yongho Seo
- Department of Nanotechnology and Advanced Materials Engineering and HMC, Sejong University, Seoul, 05006, South Korea
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Zhang B, Xia R, Yan Y, Liu J, Guan Z. Highly Transparent and Zirconia-Enhanced Sol-Gel Hybrid Coating on Polycarbonate Substrates for Self-Cleaning Applications. MATERIALS (BASEL, SWITZERLAND) 2023; 16:3138. [PMID: 37109973 PMCID: PMC10143070 DOI: 10.3390/ma16083138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/08/2023] [Accepted: 04/14/2023] [Indexed: 06/19/2023]
Abstract
To improve the efficacy of polymer-based substrate hybrid coatings, it is essential to simultaneously optimize mechanical strength and preserve the optical properties. In this study, a mixture of zirconium oxide (ZrO2) sol and methyltriethoxysilane modified silica (SiO2) sol-gel was dip-coated onto polycarbonate (PC) substrates to form zirconia-enhanced SiO2 hybrid coatings. Additionally, a solution containing 1H, 1H, 2H, and 2H-perfluorooctyl trichlorosilane (PFTS) was employed for surface modification. The results show that the ZrO2-SiO2 hybrid coating enhanced the mechanical strength and transmittance. The average transmittance of the coated PC reached up to 93.9% (400-800 nm), while the peak transmittance reached up to 95.1% at 700 nm. SEM images and AFM morphologies demonstrate that the ZrO2 and SiO2 nanoparticles were evenly distributed, and a flat coating was observed on the PC substrate. The PFTS-modified ZrO2-SiO2 hybrid coating also exhibited good hydrophobicity (WCA, 113°). As an antireflective coating on PC, with self-cleaning capability, the proposed coating has application prospects in optical lenses and automotive windows.
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Zhang C, Zhao H, Su Y, Wang H, Shen J, Wang X. Embedding constructed refractive index graded antireflective coating with high abrasion resistance and environmental stability for polycarbonate glass. J Colloid Interface Sci 2022; 608:13-21. [PMID: 34626961 DOI: 10.1016/j.jcis.2021.09.152] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 09/24/2021] [Indexed: 11/28/2022]
Abstract
Polycarbonate (PC) is a durable and transparent optical plastic material commonly used as shatter-resistant alternative to traditional optical glass. Broadband antireflective (AR) coatings with excellent mechanical strength and environmental stability are essential for PC to achieve high light transmission and visual quality. In this work, chloroform vapor treatment was employed to partially embed the silica coating into the PC substrate for adhesion enhancement, which also divided the silica coating layer into bottom and middle layers with different refractive indices. The contact between the silica nanoparticles and the substrate was transformed from "point-contact" to "area-contact", which enhanced the adhesion between coating and PC substrate. After the deposition of a top layer coating consisted of silica nanoparticles with smaller diameter, a triple-layer refractive index graded AR structure was constructed. Hexamethyldisilazane vapor surface modification was performed to decrease the surface free energy of top coating layer. The triple-layer coating coated PC exhibits superior antireflection property with an average reflectance of only 0.43% over a wide wavelength range of 400-1000 nm. After 100 times of friction or 5 months of exposure to a contaminated environment, the reflectance of coated PC shows barely noticeable difference, indicating its excellent mechanical strength and environmental stability.
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Affiliation(s)
- Chen Zhang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Huiyue Zhao
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Yixuan Su
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Hongqiang Wang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Jun Shen
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, PR China.
| | - Xiaodong Wang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, PR China.
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Cho WS, Park JY, Baek S, Choi CS, Cho SH, Hong K, Lee JL. Completely Hazy and Transparent Films by Embedding Air Gaps for Elimination of Angular Color Shift in Organic Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2021; 13:39660-39670. [PMID: 34387461 DOI: 10.1021/acsami.1c10273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Red, green, and blue top-emission organic light-emitting diodes (RGB TOLEDs) suffer from white color change with viewing angle due to the microcavity effect, called white angular dependence (WAD). Great efforts are devoted by applying various kinds of hazy films, but they suffer from poor mechanical stability and optical transmittance. Herein, we introduce an air-gap-embedded hazy film (AEHF) to solve these problems and suppress WAD in RGB TOLEDs. The AEHF is designed with optical simulation to realize high haze with transparency. By tuning geometries of the air gap inside the polymer, the AEHF realizes high haze of more than 90% in all RGB colors while maintaining high transparency. To experimentally demonstrate the AEHF, the O2 plasma is treated on a polymer film with AgCl as an etching mask to fabricate microstructures with high aspect ratios. Afterward, PDMS is coated on the patterned surface; air gaps develop spontaneously in the valleys between microstructures during the coating process. Using these processes, an air gap with 1.2 μm size and 400 nm period is formed inside the film and ∼100% haze is achieved while maintaining a high transmittance of 88%; these results agree well with rigorous coupled wave analysis results. By utilizing the AEHF into TOLEDs, the WAD can be drastically suppressed by 95.2% compared with that of a device without AEHF.
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Affiliation(s)
- Won Seok Cho
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Korea
| | - Jae Yong Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Korea
| | - Sangwon Baek
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Korea
| | - Chung Sock Choi
- Samsung Display Co., Ltd., Giheung-Gu, Yongin, Gyeonggi-do 446-711, Korea
| | - Sang-Hwan Cho
- Samsung Display Co., Ltd., Giheung-Gu, Yongin, Gyeonggi-do 446-711, Korea
| | - Kihyon Hong
- Department of Materials Science and Engineering, Chungnam National University (CNU), Daejeon 34134, Korea
| | - Jong-Lam Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Korea
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Cho WS, Park JY, Choi CS, Cho SH, Baek S, Lee JL. Air-gap-embedded robust hazy films to reduce the screen-door effect in virtual reality displays. NANOSCALE 2020; 12:8750-8757. [PMID: 32141458 DOI: 10.1039/c9nr10615d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report a way to make an air-gap-embedded flexible film to reduce the screen-door effect (SDE) in virtual reality (VR) displays. Oxygen plasma was treated with a polyethylene terephthalate substrate to produce wavelength-scale micropatterns. These micropatterns induce an effective haze, but it is easily destroyed by a very small external scratch. Such a problem could be solved by coating the patterns with poly(dimethylsiloxane) (PDMS). The viscosity of PDMS, controlled by the ratio of the base and curing agents, plays a key role in determining the size of air-gaps at the valleys of micropatterns. As the ratio of base agent increases to 40, the average haze abruptly increased from 0.9% to 88.6% in visible wavelengths, while the average total transmittance maintained was between 89.8 and 91.7%. The origin of air-gap-induced haze is confirmed by numerical simulations. The hazy film remarkably reduced the SDE of the VR display from 30.27% to 4.83% for red color, from 21.82% to 2.58% for green, and from 26.02% to 3.38% for blue, as the size of air-gaps increases from 0 to 406 ± 91 nm. No defects were found after 10 000 bending cycles with a bending radius of 3 mm.
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Affiliation(s)
- Won Seok Cho
- Graduate Institute of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
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Park JY, Kim BJ, Yoo CJ, Dong WJ, Lee I, Kim S, Lee JL. Subwavelength-scale nanorods implemented hexagonal pyramids structure as efficient light-extraction in Light-emitting diodes. Sci Rep 2020; 10:5540. [PMID: 32218542 PMCID: PMC7098980 DOI: 10.1038/s41598-020-62257-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Accepted: 02/19/2020] [Indexed: 11/22/2022] Open
Abstract
Subwavelength-scale nanorods were implemented on the hexagonal pyramid of photochemically etched light-emitting diodes (LEDs) to improve light extraction efficiency (LEE). Sequential processes of Ag deposition and inductively coupled plasma etching successfully produce nanorods on both locally unetched flat surface and sidewall of hexagonal pyramids. The subwavelength-scale structures on flat surface offer gradually changed refractive index, and the structures on side wall of hexagonal pyramid reduce backward reflection, thereby enhancing further enhancement of the light extraction efficiency. Consequently, the nanorods implemented LED shows a remarkable enhancement in the light output power by 14% compared with that of the photochemically etched LEDs which is known to exhibit the highest light output power. Theoretical calculations using a rigorous coupled wave analysis method reveal that the subwavelength-scale nanorods are very effective in the elimination of TIR as well as backward reflections, thereby further enhancing LEE of the LEDs.
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Affiliation(s)
- Jae Yong Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Buem Joon Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Chul Jong Yoo
- Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Wan Jae Dong
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Illhwan Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Sungjoo Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea
| | - Jong-Lam Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea.
- Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea.
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Ag-fiber/graphene hybrid electrodes for highly flexible and transparent optoelectronic devices. Sci Rep 2020; 10:5117. [PMID: 32198465 PMCID: PMC7083935 DOI: 10.1038/s41598-020-62056-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/02/2020] [Indexed: 11/08/2022] Open
Abstract
Transparent conducting electrodes (TCEs) have attracted considerable attention towards the development of flexible optoelectronic devices. In this study, mixed-dimensional TCEs are fabricated based on the two-dimensional graphene and one-dimensional electrospun metal fiber that can address the shortcomings of each electrode. In comparison with other TCEs, the Ag fiber/graphene hybrid electrodes exhibited a highly stable morphology (67% lower peak-to-valley ratio), low sheet resistance (approximately 11 Ω/sq), high transmittance (approximately 94%), high oxidation stability with excellent flexibility, and outstanding chemical stability. The multiple functionalities of the transparent and flexible hybrid structure highlight its potential for applications in emerging electronics and highly stable optoelectronics.
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Kim S, Yoo CJ, Park JY, Baek S, Cho WS, Lee JL. Nano-imprinting of refractive-index-matched indium tin oxide sol-gel in light-emitting diodes for eliminating total internal reflection. RSC Adv 2018; 8:37021-37027. [PMID: 35557782 PMCID: PMC9089158 DOI: 10.1039/c8ra06773b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Accepted: 10/20/2018] [Indexed: 11/21/2022] Open
Abstract
Refractive-index (RI)-matched nanostructures are implemented in GaN-based light-emitting diodes (LEDs) for enhancing light output efficiency. The RI-matched indium tin oxide (ITO) nanostructures are successfully implemented in GaN-based lateral LEDs by using ITO sol–gel and nanoimprint lithography. The ITO sol–gel nanostructures annealed at 300 °C have RI of 1.95, showing high transparency of 90% and high diffused transmittance of 34%. Consequently, the light output power in LEDs with the RI-matched nanostructures increases by 8% in comparison with that in LEDs containing flat ITO. Ray tracing and finite-difference time-domain (FDTD) simulations show that the RI-matched nanostructures on the transparent current spreading layer dramatically reduce Fresnel reflection loss at the interface of the current spreading layer with the nanostructure and extract confined waveguide lights in LEDs. Refractive-index (RI)-matched nanostructures are implemented in GaN-based light-emitting diodes (LEDs) for enhancing light output efficiency.![]()
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Affiliation(s)
- Sungjoo Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea
| | - Chul Jong Yoo
- Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea
| | - Jae Yong Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea
| | - Sangwon Baek
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea
| | - Won Seok Cho
- Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea
| | - Jong-Lam Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea .,Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea
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