A blue organic light emitting diode

A blue organic light emitting diode (OLED) which has a structure like an SH -B type diode has been developed. The blue OLED consists of a hole-injectio n layer (m-MTDATA), a hole-transporting emissive layer, a hole-blocking lay er and an electron-injection layer (Alq(3)) formed on an ITO anode by vacuu m vapor deposition. alpha-NPD was used for the hole-transporting emissive l ayer, which has an emission peak at around 455 nm. For the hole-blocking la yer, we found that 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocupr oine) is a very effective material. As Bathocuproine has a good hole-blocki ng ability, the recombination area is in the alpha-NPD layer. The electrolu minescence peak from the new blue OLED is at around 455 nm. The color coord inate in CIE chromaticity is (0.15, 0.16). The blue OLED has a potential of over 10,000 cd/m(2) at 9.5 V under DC operation with an AlLi cathode. When this OLED is driven under a 1/100 duty ratio, the peak luminance is over 5 4,000 cd/m(2). The luminous efficiency was 1.1 lm.W at 150 cd/m(2). The blu e OLED device is also a good green device without the Bathocuproine layer T he green OLED shows electroluminescence from the Alq(3) layer with luminanc e of 40,000 cd/m(2) at 10 V under DC operation, and the color coordinate in CIE chromaticity is (0.33, 0.55).