. | . |
Atomically thin light-emitting device opens the possibility for 'invisible' displays by Staff Writers Berkeley CA (SPX) Mar 30, 2018
UC Berkeley engineers have built a bright-light emitting device that is millimeters wide and fully transparent when turned off. The light emitting material in this device is a monolayer semiconductor, which is just three atoms thick. The device opens the door to invisible displays on walls and windows - displays that would be bright when turned on but see-through when turned off - or in futuristic applications such as light-emitting tattoos, according to the researchers. "The materials are so thin and flexible that the device can be made transparent and can conform to curved surfaces," said Der-Hsien Lien, a postdoctoral fellow at UC Berkeley and a co-first author along with Matin Amani and Sujay Desai, both doctoral students in the Department of Electrical Engineering and Computer Sciences at Berkeley. The device was developed in the laboratory of Ali Javey, professor of Electrical Engineering and Computer Sciences at Berkeley. In 2015, Javey's lab published research in the journal Science showing that monolayer semiconductors are capable of emitting bright light, but stopped short of building a light-emitting device. The new work in Nature Communications overcame fundamental barriers in utilizing LED technology on monolayer semiconductors, allowing for such devices to be scaled from sizes smaller than the width of a human hair up to several millimeters. That means that researchers can keep the thickness small, but make the lateral dimensions (width and length) large, so that the light intensity can be high. Commercial LEDs consist of a semiconductor material that is electrically injected with positive and negative charges, which produce light when they meet. Typically, two contact points are used in a semiconductor-based light emitting device; one for injecting negatively charged particles and one injecting positively charged particles. Making contacts that can efficiently inject these charges is a fundamental challenge for LEDs, and it is particularly challenging for monolayer semiconductors since there is so little material to work with. The Berkeley research team engineered a way to circumvent this challenge by designing a new device that only requires one contact on the semiconductor. By laying the semiconductor monolayer on an insulator and placing electrodes on the monolayer and underneath the insulator, the researchers could apply an AC signal across the insulator. During the moment when the AC signal switches its polarity from positive to negative (and vice versa), both positive and negative charges are present at the same time in the semiconductor, creating light. The researchers showed that this mechanism works in four different monolayer materials, all of which emit different colors of light. This device is a proof-of-concept, and much research still remains, primarily to improve efficiency. Measuring this device's efficiency is not straightforward, but the researchers think it's about 1 percent efficient. Commercial LEDs have efficiencies of around 25 to 30 percent. The concept may be applicable to other devices and other kinds of materials, the device could one day have applications in a number of fields where having invisible displays are warranted. That could be an atomically thin display that's imprinted on a wall or even on human skin. "A lot of work remains to be done and a number of challenges need to be overcome to further advance the technology for practical applications," Javey said. "However, this is one step forward by presenting a device architecture for easy injection of both charges into monolayer semiconductors." This study was published March 26 in the journal Nature Communications. The work was funded by the National Science Foundation and the Department of Energy.
Study shows smartphones and data centers harm the environment Hamilton, Canada (SPX) Mar 06, 2018 Data centres and smartphones will be the most damaging information and communications technologies to the environment by 2040, according to new research from W Booth School's Lotfi Belkhir. At the end of winter term in 2014, Lotfi Belkhir was approached by a student taking his Total Sustainability and Management course who asked, "What does software sustainability mean?" The Entrepreneurship and Innovation Associate Professor at the W Booth School of Engineering Practice and Technology didn' ... read more
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |