title: Highly Efficient Sky-Blue Fluorescent Organic Light Emitting Diode Based on Mixed Cohost System for Thermally Activated Delayed Fluorescence Emitter (2CzPN).
abstract: The mixed cohosts of 1,3-bis(N-carbazolyl)benzene and 2,8-bis(diphenylphosphoryl)dibenzothiophene have been developed for a highly efficient blue fluorescent oragnic light emitting diode (OLED) doped with a thermally activated delayed fluorescence (TADF) emitter [4,5-di (9H-carbazol-9-yl) phthalonitrile (2CzPN)]. We have demonstrated one of the highest external quantum efficiency of 21.8% in blue fluorescent OLEDs, which is identical to the theoretically achievable maximum electroluminescence efficiency using the emitter. Interestingly, the efficiency roll-off is large even under the excellent charge balance in the device and almost the same as the single host based devices, indicating that the efficiency roll-off in 2CzPN based TADF host is related to the material characteristics, such as low reverse intesystem crossing rate rather than charge imbalance.
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University , 151-744 Seoul, South Korea.
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Sun
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University , 151-744 Seoul, South Korea.
authors.forename: Kwon-Hyeon
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University , 151-744 Seoul, South Korea.
authors.forename: Chang-Ki
authors.initials: CK
authors.lastname: Moon
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University , 151-744 Seoul, South Korea.
authors.forename: Jeong-Hwan
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University , 151-744 Seoul, South Korea.
authors.forename: Jang-Joo
authors.initials: JJ
authors.lastname: Kim
keywords: 2CzPN; OLED; TADF; mixed cohost system; sky-blue fluorescence