White OLED Combining High Efficiency With Long Life
Suyash Khiwansara
In June 2006 Konica Minolta announced its development of an OLED lighting device with the light emission efficiency and long life equivalent to that of a fluorescent lamp. Here we take a look at the features of the device.

Phosphorescent material with 100% light emission efficiency

 Currently, OLED is being developed in a variety of fields. There are two types of material in the luminous part. One is fluorescent material, already being utilized in mobile phone displays and so forth. The other is phosphorescent material, which Konica Minolta is employing in its OLED illumination devices.

These two materials differ significantly in terms of light emission efficiency. Whereas the rate for fluorescent materials is a mere 25%, phosphorescent materials allow 100% light emission efficiency (both are theoretical values). A device with high light emission efficiency offers the dual benefits of low heat generation and energy saving. In actual fact, therefore, phosphorescent material is ideal for use in illumination and displays.



Succeeded in developing blue phosphorescent material

So why is it that until now applications have favored the use of fluorescent materials? The fact is that long-life phosphorescent material was considered harder to develop, with the development of short-wave blue phosphorescent material regarded as extremely difficult. Blue, one of the three primary colors of light, is indispensable for the development of illumination that emits white-colored light.

Konica Minolta carried out research into blue phosphorescent material and succeeded in developing the best blue phosphorescent material in the world combining high light emission efficiency with long life. This was made possible by utilizing its expertise in synthesis technology acquired during the process of developing photoreceptors for color copiers and photographic film.

Focus on illumination, aim to find practical application

Illumination is the most effective way of combining this newly developed blue phosphorescent material with Konica Minolta’s expertise in design and production techniques. Until now, OLED lighting was inferior to fluorescent lamps in terms of light emission efficiency and durability. However, in laboratory experiments OLED lighting developed by Konica Minolta has achieved light emission efficiency of 64 lumens per watt and approximately 10,000 hours of life, which compares favorably with fluorescent lamps.
OLED lighting possesses many advantages not offered by fluorescent lamps – ability to emit light from a surface, thin and flexible, low heat generation, and environmentally sound – and its development by Konica Minolta has brought it much closer to practical application.

OLED white-colored light device (Konica Minolta) *2 Incandescent light bulb Fluorescent lamp LED
Light emission efficiency
(lm/W)*1 64 10 - 20 60 - 100 50 - 70
Light emission life
(hours) 10,000 Up to 3,000 5,000 - 10,000 Up to 40,000

*1 Lamp efficiency *2 Evaluated at initial luminance of 1000cd/m2, life means 50% lumen maintenance