In a recent paper published in ACS applied electronic materials, researchers invented a flexible organic LED that releases light similar to candle light, which is more comfortable to use at night Project researcher JWO Huei jou and other researchers have developed organic LEDs that emit warm white light, similar to the light produced by candles. However, these devices still emit some blue wavelengths, which may interfere with sleep because it reduces the body's melatonin secretion.
These devices are made of rigid materials and are not bendable. One option to make them flexible is to use plastic substrates, as other organic LEDs do. But plastic can't withstand repeated bending very well.
Another option is mica, a natural mineral with extreme temperature tolerance, which can be divided into flexible transparent sheets. Therefore, jou, Ying Hao Chu and colleagues want to develop a better organic LED and apply it to the mica back plate to create a flexible candle light with a long service life.
The researchers deposited a transparent indium tin oxide film on the transparent mica sheet as the anode of the LED, which can be bent 50000 times without breaking. Next, the team mixed the luminescent substance n, n '- dicarbazole-1,1' - biphenyl with red and yellow phosphorescent dyes to produce a luminescent layer. Then the layer is placed between the conductive solution with anode on one side and aluminum layer on the other side to form a flexible organic LED.
When a constant current is applied to the device, it produces bright and warm light, and its blue wavelength emission is even less than that of natural candle light. Calculations show that exposure to LED for 1.5 hours will inhibit a person's melatonin secretion by about 1.6%, while light from cold white compact fluorescent lamps will inhibit melatonin secretion by 29%. The researchers say the flexibility of their candle like organic LEDs provides an opportunity for the design of blue light free night devices.