No. 467: A new coating with a high optical refraction index to increase the brightness of organic EL (March 23, 2012)

Technology

Light emitting diode (LED) is growing widespread rapidly as interior illumination, and organic electroluminescence (Organic EL) is supposed to follow LED. The currently widespread white LED has 100-150 lm per watt, while the organic EL under development has 50-80 lm per watt. Nissan Chemical developed a new coating to increase the brightness of organic EL, and it is confident that the new coating will increase the brightness of organic EL to 100 lm per watt.

The indium tin oxide (ITO) electrode covering the light source has an optical refraction index between 1.9 and 2.1, whereas the optical refraction index of cover glass is about 1.5. Because the difference of optical refraction index between the two is so great, light emitted from a light source returns to the light source after reflecting off the glass and generates heat, resulting in extra energy consumption. The Nissan Chemical’s new coating can adjust the optical refraction index between 1.6 and 1.81 that is the middle between the optical refraction indexes of a light source and glass, making it possible to extract light from the glass effectively. Components of this new coating include a triazine-type organic polymer containing atoms of nitrogen and carbon. It has a high degree of transparency that transmits more than 90% of visible light with a wavelength longer than 400 nanometers. Organic EL illumination generates light closer to natural light than LED. The company plans to commercialize the new product in 2013.