Efficient Hybrid White Organic Light-Emitting Diodes for Application of   Triplet Harvesting with Simple Structure
  In this study, we fabricated hybrid white organic light-emitting diodes (WOLEDs) based on triplet harvesting with simple structure. All the hole transporting material and host in emitting layer (EML) of devices were utilized with same material by using N,N'-di-1-naphthalenyl-N,N'-diphenyl-[1,1':4',1":4",1"'-quaterphenyl]-4,4"'-diamine (4P-NPD) which were known to be blue fluorescent material. Simple hybrid WOLEDs were fabricated three color with blue fluorescent and green, red phosphorescent materials. We was investigated the effect of triplet harvesting (TH) by exciton generation zone on simple hybrid WOLEDs. Characteristic of simple hybrid WOLEDs were dominant hole mobility, therefore exciton generation zone was expected in EML. Additionally, we was optimization thickness of hole transporting layer and electron transporting layer was fabricated a simple hybrid WOLEDs. Simple hybrid WOLED exhibits maximum luminous efficiency of 29.3 cd/A and maximum external quantum efficiency of 11.2%. Commission Internationale de l'Eclairage (International Commission on Illumination) coordinates of (0.45, 0.43) at about 10,000 cd/m^2. 
Kyo Min Hwang, Song Eun Lee, Sungkyu Lee, Han Kyu Yoo, Hyun Jung Baek,   Jwajin Kim, Seung Soo Yoon, and Young Kwan Kim
physics.ins-det physics.optics