Organic EL lighting luminous efficiency can exceed LED?

Organic EL lighting manufacturer, founder and CTO Tian Yuansheng of Nanjing Dijon Organic Photonics Co., Ltd. delivered a speech at the "OLEDs World Summit 2012" (San Francisco, September 26-28, 2012), an international seminar on organic EL technology. In theory, organic EL has the same luminous efficiency as LEDs, while organic LED lighting can have a much higher efficiency than LEDs. He said that organic EL devices can theoretically achieve luminous efficiencies of up to 249lm/W.

Tian Yuansheng worked in the original Eastman Kodak Company in the research of organic EL. “It is a world-renowned organic EL expert” (technical staff of Japanese organic EL manufacturers). Although he is still of American nationality, he left Kodak when Kodak sold the organic EL business to LG Group, and established Nanjing Dijon Organic Optoelectronics Co., Ltd. in Nanjing (see the website report).

According to Tian Yuansheng, the theoretical limit value of the luminous efficiency of a white light-emitting organic EL device is 249 lm/W at a color temperature of 4000 K and a single-layer light emitting structure, and 184 lm/W when a tandem structure is used. The theoretical limit value is the luminous efficiency assuming that the light extraction efficiency and the internal and external quantum efficiency are all 100%. The theoretical limit of the luminous efficiency of a white LED is about 260 lm/W. If the organic EL uses a single-layer light emitting structure, the luminous efficiency can also be similar to this value. Organic EL is also called organic light-emitting diode (OLED). There is no fundamental difference from LED in terms of light emission. From this point of view, it is not surprising that the theoretical values ​​of their luminous efficiency are close to each other.

In the organic EL devices actually produced heretofore, there have been cases where the internal quantum efficiency is close to 100%. However, the light extraction efficiency is only about 60% at the most, and it has not paved the way for improvement to 100%.

Moreover, Tian Yuansheng said that when comparing lighting fixtures for organic EL and LED, "even with the current organic EL technology, the luminous efficiency of lighting fixtures can compete with LED lighting." Tian Yuansheng quoted the DOE MultiyearPlan report published by the DOE in March 2010. "Before 2009, LED lighting has a luminous efficiency of only 32.3% of the LED light source (package)" Note 1). Exposure of the LED light source to the lighting device may cause eye damage, and the diffusion plate used to prevent this may cause the luminous efficiency to decrease. Organic EL lighting often uses light-emitting panels directly as lighting fixtures, which rarely causes a significant reduction in luminous efficiency.

Note 1) However, the future development goal listed in this DOE report is to increase the luminous efficiency of LED lighting fixtures to 62.9% of LED light sources.

In addition, Nanjing Disheng Organic Optoelectronics is currently advancing the business of specializing in the development of organic EL lighting. The performance of a luminous efficiency of 45 lm/W and a color rendering index CRI of over 90 has now been achieved on a 200 mm square panel.