#bandgap

New strategy proposed for bandgap engineering and maintaining material properties under high pressure

Prof. Ding Junfeng and his team from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Science, together with Prof. Zhang Genqiang from the University of Science and Technology of China, have achieved band gap optimization and photoelectric response enhancement of carbon nitride in the nitrogen vacancy graphite phase under high pressure.

Their results were published in the journal Physical Review Applied.

Graphitic carbon nitride (g-C3N4) has performed well in many fields, such as high-efficiency photocatalytic hydrogen production and water oxidation. However, the wide band gap of 2.7 eV of the original g-C3N4 limits its light absorption in the visible region. High pressure technology is an effective strategy to change the properties while remaining composition. Therefore, band gap engineering of g-C3N4 by high-pressure technology can significantly enhance its photocatalytic activity and improve its application potential.

In this study, the researchers prepared N-containing vacancy defect g-C3N4 nanosheets with a nitrogen/carbon ratio of 9:10 by alkali assisted thermal polymerization.

Solving the mystery of ultralow-voltage LEDs

Light-emitting diodes (LEDs) have created far-reaching impacts on display and lighting industries. For a LED to emit light, the minimum voltage is widely considered to be equal to the bandgap voltage of the material, in consideration of the energy conservation principle. Reducing the operating voltages of LEDs can save power and improve speed. 

In recent years, light emission at sub-bandgap voltages (typically 80-100% of the bandgaps) was observed for some emerging classes of LEDs, including organic LEDs (OLEDs), perovskite LEDs and quantum-dot LEDs. These observations were explained using material-specific mechanisms such as thermally-assisted upconversion and exciton-exciton annihilation, etc. These were proposed to offer small energy gains to overcome the "energy barrier" between the applied voltage and the bandgap. However, the fundamental questions of what the lowest possible voltages for LEDs really are, and whether they arise from the same physical origin, remain unanswered.

Recently, a research team led by Prof. Di Dawei at the College of Optical Science and Engineering of Zhejiang University discovered that light emission from LEDs can be observed at record-low voltages of 36–60% of the bandgaps. The results were collected, using a high-sensitivity photon detection system, from 17 types of LEDs based on perovskite, organic, quantum-dot and commercial III-V semiconductors. These voltages were too low to be explained by the previously reported mechanisms, and they revealed a universal origin of low-voltage LED operation. The research was carried out in collaboration with Prof. Sir Richard Friend at the Cavendish Laboratory of Cambridge University. A paper entitled "Ultralow-voltage operation of light-emitting diodes" was published by the researchers recently in Nature Communications.

The Story of Cadmium Telluride: Kick-Starting the Solar Boom

Boron is a versatile non-metal element, but until the last five years, chemists have only theorized about the useful properties and applications of two-dimensional (2D) boron-containing materials. In a study published this month in the Journal of Materials Chemistry A, a group led by researchers from the University of Tsukuba brought theory to life by preparing the first 2D boron monosulfide (BS) nanosheets, which can be handled layer-by-layer to control their electronic properties.

The inherently large surface areas and diverse electronic states of 2D materials make them good candidates for applications in batteries and other devices. Moreover, combining 2D building blocks into novel materials can allow for greater control over their functionalities. Previous computational studies had suggested that BS in particular could adopt several stable 2D structures with unique properties. Therefore, the researchers fabricated a 1:1 boron:sulfide bulk material, which had a rhombohedral (a three-dimensional rhombus) crystal structure (r-BS), and then stripped away individual nanolayers (2D BS), which maintained the original material's crystalline arrangement.

"Our analysis confirmed what our own calculations had predicted," says research group leader, Professor Takahiro Kondo. "That is, BS nanosheets had a different bandgap energy than the bulk material, and importantly, the bandgap could be tuned based on the number of stacked 2D BS sheets."

A Tiny New Heat Engine With No Moving Parts Just Hit an Incredible Energy Milestone

Scientists are hopeful that solid-state thermophotovoltaic (TPV) cells with no moving parts can achieve higher efficiencies at higher temperatures when it comes to converting heat into electricity – and lead the way to power grids based entirely on renewables. One such TPV cell has now hit a new world record of 40 percent efficiency, researchers report. That’s better than the steam turbines…

Wide Bandgap (SiC / GaN) power devices market 2020 – Infineon, Rohm, Mitsubishi, STMicro, Fuji – TheCoinGossip

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Simulation and Analysis of III V Characteristic and Bandgap Design for Heterojunction Laser Diode

by Thu Rein Ye Yint Win | Tin Tin Hla ""Simulation and Analysis of III-V Characteristic and Bandgap Design for Heterojunction Laser Diode""

Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019,

URL: https://www.ijtsrd.com/papers/ijtsrd26542.pdf  

Paper URL: https://www.ijtsrd.com/engineering/electronics-and-communication-engineering/26542/simulation-and-analysis-of-iii-v-characteristic-and-bandgap-design-for-heterojunction-laser-diode/thu-rein-ye-yint-win

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