Panasonic Corporation has developed a white OLED with the world's highest luminous efficiency*1 of 114 lm/W (light-emitting area of 1 cm²). In addition, a luminous efficiency of 110 lm/W has also been achieved with a device with a larger emitting area of 25 cm².
In order to achieve such a level of high efficiency with the OLED, the company focused on "light extraction technology" and the "all phosphorescent white OLED technology" (technology for the multilayering of the organic emitting layer).
OLEDs are capable of emitting any color including white when a voltage is applied by combining organic materials that emit various colors such as red, green, and blue. The soft surface luminescence makes OLEDs suitable for lighting a wide area, and along with the benefits of being not overly bright when viewed directly and a thin and lightweight structure, they are receiving attention as the next generation light source. Lighting devices equipped with the high efficiency OLEDs are considered to achieve a luminous efficiency comparable to or higher than that of fluorescent lamps (approx. 60-80 lm/W) or LED lighting fixtures (approx. 80 lm/W) currently available in the market. Further, a wide variety of applications are expected for OLED devices, including use in general lighting. White OLED lighting will create new value in people's daily lives and has great potential for realizing a comfortable and ecological lifestyle.
This development contains the following features:
1. Approximately 2.5 times improvement*2 in the light extraction efficiency (light extraction efficiency of about 50%)
2. Simultaneous achievement of high efficiency and long lifetime*3 (over 100,000 hours)
These features have been achieved with the following technologies:
1. Built-up Light Extraction Substrate (BLES) technology by the optimized arrangement of the film, glass and air for the suppression of light confinement in the OLED.
2. Optimal design of stacked organic emitting layers with high-efficiency phosphorescent materials.
Typically, the organic light emitting layers have higher refractive indices than those of a glass used for substrate and air, and only about 20% of the total generated light can be extracted because of the total internal reflection at interfaces. Although a variety of technologies have been developed, including a light extraction film attached onto the substrate and a light-scattering structure placed between organic layers and the substrate, the light extraction efficiency stayed below 40%.
Panasonic holds 30 patents in Japan and 17 overseas patents (including those pending) for this development.
The technologies obtained from the development will be announced at The Society for Information Display (SID) 2013, the world's largest conference on displays, held on May 21-24 in Vancouver, Canada. The development was conducted in the "Fundamental Technology Development of Next Generation Lighting of High-efficiency and High-quality" project since March 2010 under a contract with the New Energy and Industrial Technology Development Organization, with Idemitsu Kosan Co., Ltd, TAZMO CO., LTD., Choshu Industry Co., Ltd., Yamagata University, and Aoyama Gakuin University. The high-efficiency phosphorescent materials were provided by the Universal Display Corporation of the United States.
The Newly Developed White OLED with the World's Highest Luminous Efficiency*1
1. Luminous flux (unit: lumen) per watt of supplied power for driving at the brightness of 1,000 cd/m². The panel thickness was 2 mm or below. (As of May 24, 2013 by the company)
2. Relative to the standard OLED device (without light extraction film)
3. Time until reaching half the brightness value when driving at initial brightness of 1,000 cd/m²
