Triplet Harvesting in Hybrid White Organic Light-Emitting Diodes

• Published in: Advanced functional materials 2009-05, Vol.19 (9), p.1319-1333
• Main Authors: Schwartz, Gregor, Reineke, Sebastian, Rosenow, Thomas Conrad, Walzer, Karsten, Leo, Karl
• Format: Article
• Language: English
• Subjects: blue fluorescence; power efficiency; triplet energy; white organic light-emitting diodes
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200801503

White organic light‐emitting diodes (OLEDs) are highly efficient large‐area light sources that may play an important role in solving the global energy crisis, while also opening novel design possibilities in general lighting applications. Usually, highly efficient white OLEDs are designed by combining three phosphorescent emitters for the colors blue, green, and red. However, this procedure is not ideal as it is difficult to find sufficiently stable blue phosphorescent emitters. Here, a novel approach to meet the demanding power efficiency and device stability requirements is discussed: a triplet harvesting concept for hybrid white OLED, which combines a blue fluorophor with red and green phosphors and is capable of reaching an internal quantum efficiency of 100% if a suitable blue emitter with high‐lying triplet transition is used is introduced. Additionally, this concept paves the way towards an extremely simple white OLED design, using only a single emitter layer. White organic light‐emitting diodes (OLEDs) are efficient large‐area light sources on the way to becoming a major competitor in ambient lighting applications. A particularly elegant way to reach maximum efficiency in white OLEDs is to use only two phosphors (red and green emitting) in combination with one fluorophor (blue emitting) which has a small singlet–triplet splitting. 100% internal quantum efficiency can be achieved through proper choice of materials and sophisticated device stacks.