Jou Jwo-huei, a professor in the Department of Mater­ials Science and Engineering at National Tsing Hua University (NTHU), led an R&D team in developing a table lamp using organic light-emitting diodes (OLED) with a visible color spectrum similar to candlelight. Not only does it eliminate blue light, but compared to LED lamps its light is better suited to activities requiring up-close vision. In this age of ubiquitous use of mobile phones and tablet computers, Jou wants to spread the “candlelight OLED” gospel to enable people to enjoy higher-quality light.

Candlelight OLED: No blue light hazard

When we enter Jou Jwo-huei’s lab, the overhead lighting is turned off, leaving only natural light shining into the room. Two lamps are set out on a desk, one being a conventional LED lamp and the other a candlelight OLED lamp. Looking at us through yellow spectacle lenses—which block out blue light—Jou says warmly: “Try them yourselves! What’s the difference between them?” When the LED lamp is turned on, the glaring white light forces one to squint. But one can look directly at the soft orange light of the candlelight OLED lamp without discomfort.

“The biggest difference between OLED and LED is in the light source: OLED is a planar light source while LED is a point light source,” Jou explains. The light-emitting units in an LED are smaller than a grain of salt, and the highly concentrated light rays may irritate the eyes. To use LEDs for lighting, one must first diffuse the light rays and spread them evenly. By contrast, an OLED is composed of two layers of semiconducting oxides with a layer of light-emitting material between them that is 1000 times thinner than a human hair. The even brightness of the ­planar light source is easier on the eyes.

“You can feel for yourselves—the candlelight OLED lamp isn’t hot to the touch!” says Jou with confidence. The color temperature of the candlelight OLED lamp developed by the OLED lighting R&D team at NTHU is only 1700 Kelvin, far lower than the 3000K of existing warm white light lamps. Meanwhile, the color temperature of cool white LED lamps is around 6000K, and they operate at high temperatures and emit a lot of energy. People who work in such environments can do serious harm to their eyes if they do not rest them regularly.

To protect the eyes, some LED lamps use orange‡yellow light, which at first glance appears much softer than blue‡white light. But Jou cautions that the principle behind such LED lighting is to shine blue light onto a fluorescent layer of yellow phosphor. The service life of the phosphor coating is not as long as that of the blue light LED, so that after some time it can no longer absorb blue light, leading to “blue leakage,” with more and more blue light getting out. Some people who use orange-yellow LED table lamps notice that over time the light grows increasingly blue. This may be because the orange-yellow phosphor has begun to fail, allowing more blue light to be emitted.

The candlelight OLED developed by the OLED lighting R&D team at NTHU won the 2015 Lighting Award of the International Dark-Sky Association.

Blue light: A right time and a wrong time

Jou is the first teacher in Taiwan to offer a course in engineering ethics. To prepare for this class, he began researching medical ethics. Only then did he discover the important impact of light—the usual subject of his research—on human physiology.

“I read over 1000 papers in order to get up to date with the latest medical developments.” Jou explains that when blue light is used at night, it inhibits the secretion of melatonin in the pineal gland, so that the hormone fails to fulfill its antidiuretic and anticancer functions. This causes some people to suffer “nocturia”—the need to urinate at night—and increases the risk of prostate cancer in men and breast cancer in women.

In 2014, the medical journal CA: A Cancer Journal for Clinicians carried an article entitled “Breast Cancer and Circadian Disruption from Electric Lighting in the Modern World,” which includes a discussion of the candlelight OLED that was successfully developed in 2012. The article points out that death rates from breast cancer are higher among women in industrialized nations. If there is a connection between nighttime lighting and breast cancer, then improve­ments could be made by using either lighting that varies in accordance with circadian rhythms, or the candle­light OLED invented at NTHU.

When a quantitative spectroradiometer is placed under a white LED table lamp, it shows an especially high peak for blue light.

International attention

The NTHU R&D team first created a “sunlight-style” OLED in 2009, and then developed the candlelight OLED in 2012.

These two inventions were both patented and attracted international attention. In 2010, Japanese scientist Junji Kido, the first person to invent a white OLED, made a special trip to NTHU to exchange views with the OLED lighting team. In 2015, staff from the giant Korean firm LG Chem, which manufactures OLED panels, came to Taiwan for a visit. That same year Jou Jwo-huei won the Lighting Award of the International Dark-Sky Association.

With grants from the Ministry of Economic Affairs, NTHU and Taiwan’s WiseChip Semiconductor Company began to develop mass-production capabilities for candlelight OLED. In 2018, with assistance from the First O-Lite company of Nanjing, NTHU launched the world’s first candlelight OLED table lamp.

This candlelight OLED lamp, known as the Lily Lamp, was designed by the First O-Lite Company, a collaborative partner of NTHU’s OLED lighting R&D team.

The mission: Good lighting

The Atayal indigenous community of Smangus, which was known as “the dark village” because it was the last place in Taiwan to get electricity, later suffered from severe light pollution. Once when Jou went up into the mountains to do volunteer work there, he discovered that the natural nighttime scenery and stars were obscured by bright street lights. After discussing the matter with the local pastor, a plan was made to replace them with candlelight OLED street lights.

The village is communally managed, and Jou first made his proposal in the church, introducing the ecological advantages of candlelight OLED. Work on the project only began after getting everyone’s agreement.

Tribal elder Yuraw Icyang recalls the moment when the candlelight OLED lamps were lit. “I was really moved, because the feeling was very gentle, just like when I was small and my father and adults in the community lit the resin of the Taiwan white pine.” Yuraw Icyang hopes that the experience of Smangus will help more people understand the importance of good light for health and the environment.

In Jou’s view, not only is there not enough good lighting, but genuine protection will only come from knowledge and tools that eliminate blue light hazard. This is why he published the book Embracing Darkness to promote knowledge about the use of light, and set up a Facebook fanpage on the hazards of blue light, posting videos that share medical concepts about the effects of light on sleep. He uses the “blue light hazard quantitat­ive spectroradiometer” developed and patented by NTHU to measure office lighting and LED table lamps, and he publishes quantitative data about various levels of blue light regarding the harm they may cause to the eyes, their effect on melatonin syn­thesis, and maximum safe usage times.

In collaboration with the Southern Taiwan Science Park, the OLED lighting R&D team set up the Orange Babe Technology Company to sell candlelight OLED table lamps and blue light blocking glasses. At present, because the production volume of the table lamps is low, the prices are high, but they should fall to affordable levels once production is ramped up. Jou also plans to come out with an English edition of Embracing Darkness in hopes of raising the international profile of his “illuminating” ideas and this brilliant Taiwanese invention, which he believes will be a boon to human eyes and health.             

A candlelight OLED lamp installed in a holiday cabin in the Atayal indigenous community of Smangus. The soft color of the lamplight sets off the beauty of the natural scenery. (courtesy of NTHU OLED lighting R&D team)

Candlelight OLED street lights installed in Smangus have rattan lampshades that limit light pollution by blocking the light from shining upwards. (courtesy of NTHU OLED lighting R&D team)

Smangus is the world’s first demonstration community for blue-hazard-free lighting, and in 2020 won a Taiwan Light Environment Award. (photo by Zhao Yuchen, courtesy of Coretronic Culture and Arts Foundation)