title: Morphologically and electrochemically stable bipolar host for efficient green electrophosphorescence.
abstract: A new host tBu-o-CzOXD is facilely synthesized through a simple aromatic nucleophilic substitution reaction between 3,6-di-tert-butyl-9H-carbazole and 2,5-bis(2-fluorophenyl)-1,3,4-oxadiazole. Its thermal, electrochemical, electronic absorption and photoluminescent properties are fully investigated. A high glass transition temperature (T(g)) of 149 degrees C is observed for tBu-o-CzOXD due to the introduction of bulky tert-butyl moiety, significantly higher than 97 degrees C of o-CzOXD without tert-butyl substituent. Moreover, encapsulation of tert-butyl on the 3- and 6-positions of carbazole greatly enhances the electrochemical stability as compared to o-CzOXD. Green phosphorescent OLEDs hosted by tBu-o-CzOXD show a maximum luminance of 48293 cd m(-2) at 17.1 V, a maximum current efficiency of 38.4 cd A(-1) and a maximum power efficiency of 34.7 lm W(-1). Furthermore, the devices exhibit a slow current efficiency roll-off. The device merits, together with the excellent morphological and electrochemical stability, make the new compound an ideal host material for phosphorescent emitters.
authors.affiliation: Department of Chemistry, Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Youtian
authors.initials: Y
authors.lastname: Tao
authors.forename: Shaolong
authors.initials: S
authors.lastname: Gong
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhong
authors.forename: Chuluo
authors.initials: C
authors.lastname: Yang
authors.forename: Jingui
authors.initials: J
authors.lastname: Qin
authors.forename: Dongge
authors.initials: D
authors.lastname: Ma
mesh_terms: D002227:Carbazoles / Q000737:chemistry*; D003198:Computer Simulation; D004563:Electrochemistry; D049449:Luminescence; D008163:Luminescent Measurements; D008956:Models, Chemical; D010069:Oxadiazoles / Q000737:chemistry*
chemical_list: D002227:Carbazoles; D010069:Oxadiazoles