Device could boost image quality for phones, computers and TVs

May 01, 2014 by Bill Kisliuk
Thin-film transistor developed at UCLA. Credit: UCLA Engineering

(Phys.org) —A device created by UCLA researchers could lead to a significant leap in the quality of images on smartphones, computer displays, TVs and inkjet printers.

The new material, and a new developed at UCLA, are used to produce semiconductors that are essential to and organic light-emitting diode, or OLED, displays.

Led by Yang Yang, the Carol and Lawrence E. Tannas Jr. Professor of Engineering at the UCLA Henry Samueli School of Engineering and Applied Science, the team created a high-performance device that can be produced without requiring a clean room or the expensive equipment now commonly in use.

"Our semiconductor process is faster, less expensive and more reliable than existing processes," said Yang, a professor in the school's materials science and and a member of the UCLA California NanoSystems Institute. "We strongly believe it can be used as a technology to replace existing processes and scale up production of ."

The research was published April 17 in the peer-reviewed journal Advanced Materials.

LCDs and OLEDs use millions of pixels to form text and images on the screen. Thin-film transistors, or TFTs, are the key component of the technology that controls the brightness and color provided by each pixel.

Typically, a transistor's performance is judged by electron "mobility," or the ability to precisely adjust the voltage and current that turn pixels on and off. Transistors with higher adjust the screen's color and brightness more easily and with greater energy efficiency than low-mobility devices.

Currently, amorphous silicon-based TFTs are the most popular technology in LCDs, but they suffer low mobility. This is why, when watching a baseball game on a large LCD TV, viewers can often see the "trail" of the ball when it's thrown or hit.

The UCLA-developed product, a non-silicon–based amorphous oxide semiconductor TFT, offers mobility that is 10 to 20 times greater than that of an amorphous silicon-based TFT. The device, which is composed of indium gallium zinc oxide and indium tin zinc oxide, has channels that are designed differently than those in other TFTs.

The processing technology is also different.

Currently, amorphous oxide semiconductor TFTs are prepared by a process that requires a large vacuum chamber and a costly coating procedure. UCLA researchers used a solution process, akin to applying a coat of paint to an object and then baking it in an oven.

"The improved mobility represents a breakthrough for solution-processed metal oxide TFTs," said You Seung Rim, a postdoctoral researcher in UCLA's materials science and engineering department and the lead author of the research. "Our device's performance is comparable to that of commercial TFTs, but it can be produced at a much lower cost."

Other authors include graduate student researchers Huajun Chen, Xiaolu Kou and Hsin-Sheng Duan and postdoctoral researchers Huanping Zhou and Min Cai of UCLA's and engineering department, and H.J. Kim, a professor at Yonsei University in Seoul.

Explore further: X-ray detector on plastic delivers medical imaging performance

More information: Rim, Y. S., Chen, H., Kou, X., Duan, H.-S., Zhou, H., Cai, M., Kim, H. J. and Yang, Y. (2014), "Boost Up Mobility of Solution-Processed Metal Oxide Thin-Film Transistors via Confining Structure on Electron Pathways." Adv. Mater. doi: 10.1002/adma.201400529

add to favorites email to friend print save as pdf

Related Stories

UCLA scientists double efficiency of novel solar cell

Jul 29, 2013

Nearly doubling the efficiency of a breakthrough photovoltaic cell they created last year, UCLA researchers have developed a two-layer, see-through solar film that could be placed on windows, sunroofs, smartphone ...

Recommended for you

California bans paparazzi drones

4 hours ago

California on Tuesday approved a law which will prevent paparazzi from using drones to take photos of celebrities, among a series of measures aimed at tightening protection of privacy.

User comments : 7

Adjust slider to filter visible comments by rank

Display comments: newest first

Benni
not rated yet May 01, 2014
Heads up Corning Glass, UCLA's Material Science department is about to put your TFT manufacturing division out of business.
Eikka
1 / 5 (1) May 01, 2014
Currently, amorphous silicon-based TFTs are the most popular technology in LCDs, but they suffer low mobility. This is why, when watching a baseball game on a large LCD TV, viewers can often see the "trail" of the ball when it's thrown or hit.


This is not technically true.

Current TFT televisions have response times well fast enough that no discernible "ghosting" can be seen. The real cause of the effect is that sports are live events and the video is compressed on the fly with strict bandwidth limitations because transmission networks want to cram in as many channels in their streams as possible.

With pre-recorded content, the compression algorithms "predict" what is going to happen next by simply looking ahead and adjusting the compression accordingly. With live video, it cannot. Since the video compression works by comparing differences in the frames, any sudden large movement tends to leave a fringe or a ghost behind where the object used to be.
Eikka
5 / 5 (1) May 01, 2014
Another reason for ghosting in sports broadcasts is that they like to use interlaced video to increase the apparent framerate without increasing the required bandwidth to provide smoother output, but with fast movement the two interlaced fields may capture significantly different images, and when interpolated back into a full frame in the reciever they turn up as ghosts around moving objects.
HTK
not rated yet May 01, 2014
LOL

that shut him up
KBK
5 / 5 (1) May 01, 2014
The third problem is encoding to save on cost of bits transfer. It's better than it was years or more back, but low bit encoding, where non changing bits repeat for multiple frames, this can wreak sever havoc with viewing quality.

Like all satellite and bandwidth sensitive situations, the quality will be scaled down to the point that the average person is on the verge of outright complaining. But the artifacts are well in evidence by that time.

The fewer the bits are sent per broadcast channel....the more infomercial, drivel, and schlock channels can be crammed into the same size pipe.

It's about revenue, not the purchasers; it's about taking as much as can be taken while giving as little back as is possible.
DonGateley
5 / 5 (1) May 02, 2014
"It's about revenue, not the purchasers; it's about taking as much as can be taken while giving as little back as is possible."

The fundamental principle of capitalism. It's what turns revenue into profit.
Eikka
3 / 5 (1) May 02, 2014
"It's about revenue, not the purchasers; it's about taking as much as can be taken while giving as little back as is possible."

The fundamental principle of capitalism. It's what turns revenue into profit.


And on the other hand, the consumers are trying to take as much as possible while paying as little as possible, which leads to competition - because it's better to have less profit than no customers and no profit.

All in all, things tend to balance out to the point where what you're actually getting is a compromize between efficient use of resources (bandwidth) and product quality that is good enough that you competitors can't do you one better without running up significantly in cost.

But then your capitalist corporations turn to the state and lobby laws that secure them monopolies, and then you get the barely passable products at extortion prices where the only limiting factor is that your customers are just about to complain if you make it any worse.