Organic light emitting materials and devices: From white light to near infrared

In this talk we will present our efforts in the area of white and near infrared organic light emitting diodes (OLEDs). White OLEDs are considered to have great potential in solid-state lighting and as back-lights for LCD displays. Many approaches have been reported for obtaining white OLEDs using materials such as small molecules and/or polymers. Among such approaches is the excimer OLED. We will present a modification to recent multilayer structures by employing (4',6'-difluorophenylpyridinato-N,C ^2') platinum(II) (2,4-pentanedionato-O,O') [FPt] as a single dopant, which simplifies the fabrication process and in turn lowers the production cost without sacrificing performance. In this regard, we improve the device characteristics by incorporating novel carbazolyl-pyridine based host and modifying the device architecture. The device efficiency is enhanced from a previously reported 6% to over 10%. Such device also maintains an external quantum efficiency of 8 % at a brightness of 1000 cd/m ². Additionally, a solution-processed excimer OLED and a high efficiency two-layer white OLED will be discussed. There are many avenues to be explored in the area of organic materials for infrared emission. For example, near infra-red diodes are currently employed in applications such as defense, security, telecommunications and bio-imaging. In this talk, we will present progress made in developing near infra-red OLEDs. The approach focuses on the use of heavy metal complexes as phosphorescent emitters. The choice of phosphorescent materials is due to the potential capability of harvesting both electrically generated singlet and triplet excitons (i.e., the possibility of 100% internal quantum efficiency). This presentation will include discussion related to development of novel, efficient cyclometalated Ir complexes and their use in near infra-red OLEDs. Improved device characteristics have been attained through the incorporation of novel charge-transporting and host materials, balancing charge injection and suitably confining excitons.