
An ultrathin Ag film based OLED inside Professor Jay Guo’s lab at 3537 G.G. Brown on North Campus in Ann Arbor MI on May 5, 2021. Guo’s group is systematically improving the light power distribution in OLEDs by removing the waveguide mode and optimizing the organic stacks and the ultrathin AG anode. This simple yet effective method leads to significantly enhanced performance of the external quantum efficiency of the OLED. Guo’s solution is not only simple in process but also can achieve high throughput and low cost with excellent compatibility with the large-scale manufacturing process in the display industry. In principle, the modal elimination approach introduced in this work could be extended to other solid-state light emitting diodes (LEDs) such as perovskites, quantum-dots, or III-V based LEDs since all of which are susceptible to the issue of light trapping as waveguide mode.
Image credit: Robert Coelius/University of Michigan Engineering, Communications & Marketing
A five-nanometer-thick layer of silver and copper outperforms conventional indium tin oxide without adding cost
A new electrode that could free up 20% more light from organic light-emitting diodes has been developed at the University of Michigan. It could help extend the battery life of smartphones and laptops, or make next-gen televisions and displays much more energy efficient.
“With our approach, you can do it all in the same vacuum chamber,” said L. Jay Guo, U-M professor of electrical and computer engineering and corresponding author of the study.
Unless engineers take action, about 80% of the light produced by an OLED gets trapped inside the device. It does this due to an effect known as waveguiding. Essentially, the light rays that don’t come out of the device at an angle close to perpendicular get reflected back and guided sideways through the device. They end up lost inside the OLED.
A good portion of the lost light is simply trapped between the two electrodes on either side of the light-emitter. One of the biggest offenders is the transparent electrode that stands between the light-emitting material and the glass, typically made of indium tin oxide (ITO). In a lab device, you can see trapped light shooting out the sides rather than traveling through to the viewer.
“Untreated, it is the strongest waveguiding layer in the OLED,” Guo said. “We want to address the root cause of the problem.”
By swapping out the ITO for a layer of silver just five nanometers thick, deposited on a seed layer of copper, Guo’s team maintained the electrode function while eliminating the waveguiding problem in the OLED layers altogether.
“Industry may be able to liberate more than 40% of the light, in part by trading the conventional indium tin oxide electrodes for our nanoscale layer of transparent silver,” said Changyeong Jeong, first author and a Ph.D. candidate in electrical and computer engineering.
This benefit is tricky to see, though, in a relatively simple lab device. Even though light is no longer guided in the OLED stack, that freed-up light can still be reflected from the glass. In industry, engineers have ways of reducing that reflection—creating bumps on the glass surface, or adding grid patterns or particles that will scatter the light throughout the glass.
“Some researchers were able to free up about 34% of the light by using unconventional materials with special emission directions or patterning structures,” Jeong said.
In order to prove that they had eliminated the waveguiding in the light-emitter, Guo’s team had to stop the light trapping by the glass, too. They did this with an experimental set-up using a liquid that had the same index of refraction as glass, so-called index-matching fluid—an oil in this case. That “index-matching” prevents the reflection that happens at the boundary between high-index glass and low-index air.
Once they’d done this, they could look at their experimental set-up from the side and see whether any light was coming sideways. They found that the edge of the light-emitting layer was almost completely dark. In turn, the light coming through the glass was about 20% brighter.
The finding is described in the journal Science Advances, in a paper titled, “Tackling light trapping in organic light-emitting diodes by complete elimination of waveguide modes.”
Original Article: Nanotech OLED electrode liberates 20% more light, could slash display power consumption
More from: University of Michigan
The Latest Updates from Bing News & Google News
Go deeper with Bing News on:
Organic light-emitting diodes
- Organic Light-Emitting Diode (OLED) Market Business Insights from 2023-2030
Organic Light-Emitting Diode (OLED) Market[2023-2029] research report offers an in-depth analysis of the market ...
- New Simulation Reveals Secrets of Exotic Form of Electrons called Polarons
Courtesy of F. Giustino. A new leaf has turned in scientists’ hunt for developing cutting-edge materials used in organic light-emitting diode (OLED) TV’s, touchscreens, and more. The advance involves ...
- Global OLEDoS (Organic Light-Emitting Diode on Silicon) Market Thriving Worldwide: Investment Campaigns, Trends and Analysis 2023-2028 | IRC
The research report onOLEDoS (Organic Light-Emitting Diode on Silicon) Marketpresents a comprehensive analysis of ...
- The best 4K TVs for movies, gamers, sports — and everyone else
With more options than ever, it's important to understand the features you will want to focus on in order to narrow down the best TVs for you. They used to be, but not anymore. The saturated 4K TV ...
- Global Organic Light Emitting Diode (OLED) Displays Market to Reach $347.7 Billion by 2030
The global economy is at a critical crossroads with a number of interlocking challenges and crises running in parallel. The uncertainty around how Russia`s war on Ukraine will play out this year and ...
Go deeper with Google Headlines on:
Organic light-emitting diodes
[google_news title=”” keyword=”organic light-emitting diodes” num_posts=”5″ blurb_length=”0″ show_thumb=”left”]
Go deeper with Bing News on:
OLEDs
- Samsung S95C vs Samsung S95B: which OLED TV should you buy?
Samsung is swinging for the fences with its QD-OLEDs this year, releasing two new series of TVs that boast the same Quantum Dot OLED tech as 2022’s stunning Samsung S95B QD-OLED TV. While the Samsung ...
- Fundamental science enables creation of efficient, more colorful OLEDs
The challenge of creating next-gen organic light-emitting diode (OLED) displays has been finding a way to improve color brilliance without lowering electrical efficiency. Now, researchers have found a ...
- Samsung prices its 2023 QD OLEDs (Finally, mostly…)
On the heels of its LCD pricing announcements, Samsung has finally revealed what five out of its six 2023 QD OLEDs will set you back ...
- Turning OLEDs And Acrylic Into Faux Nixie Tubes
Love ’em or hate ’em, Nixies and the retro clocks they adorn are here to stay. At least until the world’s stock of surplus Soviet tubes is finally depleted, that is. The glow discharge tubes ...
- Displays with more brilliant colors through a fundamental physical concept
New research has shown that a strong coupling of light and material increases the colour brilliance of OLED displays. This increase is independent of the viewing angle and does not affect energy ...
Go deeper with Google Headlines on:
OLEDs
[google_news title=”” keyword=”OLEDs” num_posts=”5″ blurb_length=”0″ show_thumb=”left”]