Candles can emit a comfortable, warm light. In contrast, some electric lights such as light-emitting diodes (LEDs) can give off unwanted blue light that can, for example, interfere with sleep. Safe, energy-efficient, environmentally friendly light sources that can mimic the warm glow of candlelight would, thus, be useful.
Ying-Hao Chu, National Tsing Hua University and National Yang Ming Chiao Tung University, Hsinchu, Taiwan, Jwo-Huei Jou, National Tsing Hua University, and colleagues have developed an organic LED with a plastic-free, flexible mica backing, creating a bendable light with candlelight-like characteristics and a long lifespan. The team deposited a clear indium tin oxide (ITO) film onto a transparent, freshly cleaved muscovite mica sheet. The mica substrate coated with this transparent conductor survived 50,000 bending cycles.
The researchers then mixed 4,4′-N,N‘-dicarbazole-1,1’-biphenyl with red and yellow dopants to produce a light-emitting layer. This layer was placed between electrically conductive layers with the ITO electrode on one side and an aluminum layer 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 actual candlelight. According to the researchers, the flexibility of the candlelight-like organic LED could open up design opportunities for blue-light-free devices.
- Flexible Candlelight Organic LED on Mica,
Tun-Hao Chen, Hao-Jen Chen, Ching-Yu Weng, Feng-Rong Chen, De-Shiang Liou, Sun-Zen Chen, Ying-Hao Chu, Jwo-Huei Jou,
ACS Appl. Electron. Mater. 2022.