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New Flexible Organic LED Gives Off a Comfortable Candlelight-Like Glow

A bendable organic LED with a natural mica backing emits an intense, candle-like glow. Photo credits: Andy Chen and Ambrose Chen

Candles emit a soft, comfortable light and create the ambiance for a special dinner or just a peaceful evening at home. Some lighting alternatives, such as B. electronic candles, however, emit unwanted light with a blue wavelength, which interferes with the lighting circadian rhythm of the body. Researchers are now reporting in the journal ACS applied electronic materials have manufactured an improved flexible organic LED that emits candlelight-like light for bendable lighting and smart displays that people can conveniently use at night.

Previously, Jwo-Huei Jou and other researchers developed organic LEDs that emit warm white light similar to that of candles. However, the devices still emitted some blue wavelengths, which can disrupt sleep because they reduce the body’s production of melatonin.

These devices were made of rigid materials and could not be bent. One way to make them flexible is to use a plastic backing like other organic LEDs do. But plastics don’t hold up well to repeated flexing. Another option for the back is mica – a natural mineral with extreme temperature tolerance that can be cleaved into flexible, transparent sheets. So Jou, Ying-Hao Chu and colleagues set out to develop an even better organic LED and put it on a mica backing to create a bendable, long-life candle-like light.

As the anode of the LED, the researchers deposited a clear indium tin oxide film on a transparent mica sheet that could be flexed 50,000 times without breaking. Next, the team mixed the phosphor N,N’-Dicarbazole-1,1′-biphenyl with red and yellow phosphorescent dyes to produce a light-emitting layer. This layer was then sandwiched between electrically conductive solutions with the anode on one side and a layer of aluminum on the other side, creating a flexible organic LED.

When a constant current was applied to the device, it produced a bright, warm light with even fewer blue wavelength emissions than natural candlelight. Calculations showed that a 1.5 hour exposure to the LED would suppress a person’s melatonin production by approximately 1.6%, while the light from a cool white CFL would suppress melatonin production by 29%. The researchers say the flexibility of their candlelight-like organic LED opens up the design possibilities for blue-light-free night time devices.

Reference: “Flexible Candlelight Organic LED on Mica” by Tun-Hao Chen, Hao-Jen Chen, Ching-Yu Weng, Feng-Rong Chen, De-Shiang Liou, Sun-Zen Chen, Ying-Hao Chu, and Jwo-Huei Jou , May 9, 2022, ACS applied electronic materials.
DOI: 10.1021/acsaelm.2c00123

The authors acknowledge funding from the Ministry of Science and Technology (Taiwan, Republic of China).

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New Flexible Organic LED Gives Off a Comfortable Candlelight-Like Glow Source link New Flexible Organic LED Gives Off a Comfortable Candlelight-Like Glow

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