Giving off a soft comfortable glow, candles set the ambiance for a special dinner or just a peaceful evening at home. However, some lighting alternatives, such as electronic candles, give off unwanted blue wavelength light that interferes with the body’s circadian rhythm. Now, researchers reporting in the journal ACS Applied Electronic Materials have fabricated an improved flexible organic LED that releases candlelight-like light for bendable lighting and smart displays that people can comfortably use at night.

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

These devices were made of rigid materials and weren’t bendable. One option for making them flexible is to use a plastic backing, as has been done for other organic LEDs. But plastics don’t hold up well to repeated bending. Another option for the backing is mica — a natural mineral with extreme temperature tolerance that can be split into bendable, transparent sheets. So, Jou, Ying-Hao Chu, and colleagues wanted to develop an even better organic LED and apply it to a mica backing, creating a bendable candle-like light with a long lifespan.

The researchers deposited a clear indium tin oxide film onto a transparent mica sheet as the LED’s anode, which could bend 50,000 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 light-emitting layer. This layer was then placed between electrically conductive solutions with the anode 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 less blue wavelength emissions than natural candlelight. Calculations showed that exposure to the LED for 1.5 hours would suppress a person’s melatonin production by about 1.6%, whereas light from a cold-white compact fluorescent lamp would suppress melatonin production by 29%. The researchers say that the flexibility of their candlelight-like organic LED opens up the design opportunities for blue-light-free nighttime devices.

Organic LED is a type of lighting technology that uses natural materials to create light. In general, it is made from a gas-permeable polymer, but in some cases can be created with a liquid solution. Organic LEDs are considered eco-friendly because they do not contain toxic chemicals or heavy metals.

The continuous commercial market is quickly becoming a more affordable place to buy flexible organic LED (FOLE) products. The prices for these products have come down considerably in recent years, and this trend is expected to continue. In fact, some of the best flexible organic LED products are now available at a fraction of the price of traditional lighting products.

One reason for this cost reduction is that FOLE technology has been improving rapidly. In the past, LED technology was expensive and required large quantities of materials to produce a single lightbulb. However, current technologies allow for smaller LED lights with lower energy consumption. This means that FOLE products can be produced in larger quantities, which reduces the cost. Additionally, FOLE lights use less energy than traditional bulbs, so they are environmentally friendly.

The prices for flexible organic LED products have continued to decrease in recent years, and there are now many options available at very affordable prices. Many of these products are now available at or below the cost of traditional lighting products. For example, Cree’s XLamp XP-G2 LED product is available for just $8 per light bulb. This is much cheaper than traditional bulbs, which can cost up to $25 per light.