White Organic LED Has Single Emission Layer

Researchers at Academia Sinica in Taipei, Taiwan, have fabricated a bright-white organic LED with a single emission layer. With a simple three-layer structure, the device generated white light with maximum brightness approaching 42,000 cd/m² at 14 V and maximum luminance efficiency of 2.92 lm/W at 6.5 V. CIE coordinates remained virtually constant (0.31, 0.33) even with a voltage increase from 8 to 12 V. A two-layer structure with the same type of emission layer also produced stable white color, which the researchers attribute to the confinement of the charge recombination zone in one layer. The work is described in the Dec. 9 issue of Applied Physics Letters.