A quick operating organic EL device using Ru complex light-emitting layer with 2,5-bis(4-tert-butyl-2-benz-oxazolyl) thiophene electron transport layer

Recently, solid-state light-emitting devices based on small molecules such as Ru(bpy)3(PF6)2 and its derivatives attracted attention as electro luminescence (EL) materials because the luminance shows as high as l600 cd m−2 at only 5 V with spin-cast films in air without sealing the devices. Devices based on these materials operate at low voltage (2.5–5 V), however, response of light emission after applying voltage is rather slow, suggesting a similar mechanism with liquid electro-generated chemiluminescence (ECL) cells. In this paper, we added thin electron transporting layer, 2,5-bis(5-tert-butyl-2-benz-oxazolyl) thiophene (BBOT) film (ca. 200 nm) between Ru complex light-emitting layer and Al electrode. As a result, much quicker response was achieved than the ruthenium(II) complex EL devices without adding the BBOT electron transporting layer.