Double co-host emitter based top emitting white organic light emitting diodes with enhanced brightness and efficiency

Novel and simplified bi-layer top-emitting white organic light emitting diodes (OLEDs) with dual co-host emitters have been simulated and analyzed. They consist of yellow-green emitting layer (EML) as electron transport layer (ETL) and blue EML as hole transport layer (HTL). Novelty of the device lies in simplification of tri-layer white OLED to a bi-layered device which is done by merging yellow-green EML with ETL and blue EML with HTL. The simulated devices show Commission Internationale de L’Eclairage (CIE) colour coordinates well within the emission range of white light. The results show that device A with 5,6,11,12-tetraphenylnaphthacene (rubrene) doped ETL has achieved the lowest luminance but longest excited state lifetime. Device D with tris-(8-hydroxyquinoline) aluminum: 4-(dicyanomethylene)-2-t-butyle-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)4H-pyran (Alq3: DCJTB) as ETL which emits yellow light and 2, 7-bis [N, N-bis (4-methoxy-phenyl) amino]-9, 9-spirobifluorene (MS-TPD): bis(2-methyl-8-quninolinato)-4-phenylphenolate alu-minium (BAlq) as HTL which is responsible for blue light emission is found to have best characteristics when compared to other simulated devices. It has a maximum luminance of 10 000 cd/m2 and current efficiency of 15.25 cd/A, respectively, and CIE coordinates are at (0.329, 0.319). The device is found to be compatible to be used in solid state lighting applications because of the low driving voltage of the device.