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Optoelectronic Devices: 2021

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Optical and Photonic Materials".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 10254

Special Issue Editor


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Guest Editor
Institute of Electro-Optical Science and Technology, National Taiwan Normal University, No.88, Sec. 4, Ting-Chou Rd., Taipei 11677, Taiwan
Interests: optoelectronic semiconductor materials and devices; nano-fabrication process; green energy technology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The demand for optoelectronic devices, relying on light-matter interactions to convert photons into electrons or vice versa, have considerably grown as their related applications continue to dominate a vast variety of consumer products used in our daily life. This Special Issue seeks original submissions in developing novel optoelectronic devices, and the research topics cover but not are not limited to the following: new techniques for the growth, heterogeneous integration, and characterization of optical materials and optoelectronic devices for the applications in solar cells, LEDs, and lasers devices. Fabrication, characterization, and material properties of various photonic platforms, such as III-V and group-IV optoelectronics, nanostructures, 2D materials, etc. are also included. Advanced concepts, rather than the established designs for new applications, such as nanophotonics, microcavity polaritons, metamaterials, and topological photonics and materials explore the fundamentals of light-matter interactions, and consequently enhance performances of optoelectronic devices.

Prof. Dr. Ya-Ju Lee
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • compound semiconductors
  • nanophotonics
  • 2D materials
  • microcavity polaritons
  • solar cells
  • light-emitting diodes
  • lasers

Published Papers (4 papers)

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Research

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8 pages, 2069 KiB  
Article
Strain Compensation and Trade-Off Design Result in Exciton Emission at 306 nm from AlGaN LEDs at Temperatures up to 368 K
by Shih-Ming Huang, Mu-Jen Lai, Rui-Sen Liu, Tsung-Yen Liu and Ray-Ming Lin
Materials 2021, 14(21), 6699; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14216699 - 07 Nov 2021
Cited by 1 | Viewed by 1801
Abstract
In this study, we suppressed the parasitic emission caused by electron overflow found in typical ultraviolet B (UVB) and ultraviolet C (UVC) light-emitting diodes (LEDs). The modulation of the p-layer structure and aluminum composition as well as a trade-off in the structure to [...] Read more.
In this study, we suppressed the parasitic emission caused by electron overflow found in typical ultraviolet B (UVB) and ultraviolet C (UVC) light-emitting diodes (LEDs). The modulation of the p-layer structure and aluminum composition as well as a trade-off in the structure to ensure strain compensation allowed us to increase the p-AlGaN doping efficiency and hole numbers in the p-neutral region. This approach led to greater matching of the electron and hole numbers in the UVB and UVC emission quantum wells. Our UVB LED (sample A) exhibited clear exciton emission, with its peak near 306 nm, and a band-to-band emission at 303 nm. The relative intensity of the exciton emission of sample A decreased as a result of the thermal energy effect of the temperature increase. Nevertheless, sample A displayed its exciton emission at temperatures of up to 368 K. In contrast, our corresponding UVC LED (sample B) only exhibited a Gaussian peak emission at a wavelength of approximately 272 nm. Full article
(This article belongs to the Special Issue Optoelectronic Devices: 2021)
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13 pages, 4082 KiB  
Article
Substituent-Adjusted Electrochromic Behavior of Symmetric Viologens
by Qun Zhang, Li Yuan, Fanglan Guan, Xin Li, Rui Wang, Jian Xu, Yanyan Qin and Guangming Chen
Materials 2021, 14(7), 1702; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14071702 - 30 Mar 2021
Cited by 3 | Viewed by 2346
Abstract
As a promising electrochromic material, viologens have attracted increasing attention due to their high redox activity and adjustable electrochromic capability. In order to investigate the effect of alkyl substituents on electrochromic behavior, four alkyl-substituted viologens and a benzyl-substituted viologen were synthesized, namely 1,1′-dioctyl-4,4′-bipyridinium [...] Read more.
As a promising electrochromic material, viologens have attracted increasing attention due to their high redox activity and adjustable electrochromic capability. In order to investigate the effect of alkyl substituents on electrochromic behavior, four alkyl-substituted viologens and a benzyl-substituted viologen were synthesized, namely 1,1′-dioctyl-4,4′-bipyridinium dibromide (OV), 1,1′-didekyl-4,4′-bipyridinium dibromide (DeV), 1,1′-didodecyl-4,4′-bipyridinium dibromide (DoV), 1,1′-dihexadecyl-4,4′-bipyridinium dibromide (HV), and 1,1′-dibenzyl-4,4′-bipyridinium dibromide (BV). The different photophysical and electrochemical properties of these viologens were attributed to their deviation in spatial structure caused by different substituents. Compared with benzyl-substituted BV, a slight blueshift occurred for the absorption peaks of alkyl-substituted viologens from 262 to 257 nm with the increase in alkyl chain length. Moreover, the first redox couple increased positively, and the dimerization of the compound decreased gradually, accompanied by the decrease in optical contrast and distinct chromatic difference. A comparison of chromatic and optical contrasts indicated that OV had the longest coloring response time (RTc), while it was shortest for HV. The bleaching response time (RTb) of viologen films gradually decreased with the alkyl chain length, and the OV film had the shortest RTb. Furthermore, when increasing the length of the alkyl chain, the cycling stabilities of alkyl viologens increased gradually. In addition, the OV film exhibited the best contrast after 200 continuous cycles. Full article
(This article belongs to the Special Issue Optoelectronic Devices: 2021)
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Review

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26 pages, 3411 KiB  
Review
Graphene as a Transparent Conductive Electrode in GaN-Based LEDs
by Hehe Zhang, Jan Mischke, Wolfgang Mertin and Gerd Bacher
Materials 2022, 15(6), 2203; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062203 - 16 Mar 2022
Cited by 12 | Viewed by 2723
Abstract
Graphene combines high conductivity (sheet resistance down to a few hundred Ω/sq and even less) with high transparency (>90%) and thus exhibits a huge application potential as a transparent conductive electrode in gallium nitride (GaN)-based light-emitting diodes (LEDs), being an economical alternative to [...] Read more.
Graphene combines high conductivity (sheet resistance down to a few hundred Ω/sq and even less) with high transparency (>90%) and thus exhibits a huge application potential as a transparent conductive electrode in gallium nitride (GaN)-based light-emitting diodes (LEDs), being an economical alternative to common indium-based solutions. Here, we present an overview of the state-of-the-art graphene-based transparent conductive electrodes in GaN-based LEDs. The focus is placed on the manufacturing progress and the resulting properties of the fabricated devices. Transferred as well as directly grown graphene layers are considered. We discuss the impact of graphene-based transparent conductive electrodes on current spreading and contact resistance, and reveal future challenges and perspectives on the use of graphene in GaN-based LEDs. Full article
(This article belongs to the Special Issue Optoelectronic Devices: 2021)
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15 pages, 4882 KiB  
Review
Progress and Challenges of InGaN/GaN-Based Core–Shell Microrod LEDs
by Johanna Meier and Gerd Bacher
Materials 2022, 15(5), 1626; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15051626 - 22 Feb 2022
Cited by 11 | Viewed by 2564
Abstract
LEDs based on planar InGaN/GaN heterostructures define an important standard for solid-state lighting. However, one drawback is the polarization field of the wurtzite heterostructure impacting both electron–hole overlap and emission energy. Three-dimensional core–shell microrods offer field-free sidewalls, thus improving radiative recombination rates while [...] Read more.
LEDs based on planar InGaN/GaN heterostructures define an important standard for solid-state lighting. However, one drawback is the polarization field of the wurtzite heterostructure impacting both electron–hole overlap and emission energy. Three-dimensional core–shell microrods offer field-free sidewalls, thus improving radiative recombination rates while simultaneously increasing the light-emitting area per substrate size. Despite those promises, microrods have still not replaced planar devices. In this review, we discuss the progress in device processing and analysis of microrod LEDs and emphasize the perspectives related to the 3D device architecture from an applications point of view. Full article
(This article belongs to the Special Issue Optoelectronic Devices: 2021)
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