High-Efficacy OLED Lighting Panel

Organic light-emitting diode (OLED) lighting is a potential candidate for application to high-quality, highefficacy flat light sources. However, most reports so far on the efficacy of white OLEDs have focused on small devices measuring approximately 2 × 2 mm. Toshiba has now developed a high-efficacy OLED lighting panel with a large luminous area.

While the internal quantum efficiency of OLEDs is considered to have already reached almost 100%, their efficacy can be further improved by reducing the drive voltage and improving the light out-coupling efficiency. In order to realize large OLED lighting panels, it is also necessary to reduce the voltage drop at the transparent anode and improve luminous uniformity. We adopted the following three approaches: (1) improvement of the outcoupling efficiency by using a highly reflective cathode, (2) reduction of the drive voltage by using a high-mobility electron transport layer, and (3) improvement of the luminous uniformity by embedding metal bus lines.

Our newly developed OLED lighting panel with a luminous area of 70 × 80 mm has achieved the world's highest-level efficacy(*) of 91 lm/W at 1 000 cd/m2. The external quantum efficiency, chromaticity coordinates, correlated color temperature, and voltage were 43.4%, (0.45, 0.42), 3 010 K, and 3.1 V, respectively.

(*) As of June 2012, at the SID International Symposium, Seminar and Exhibition, Display Week 2012 (as researched by Toshiba)

Device structure and luminous efficiency of highly efficient OLED