title: Ter(9,9-diarylfluorene)s: highly efficient blue emitter with promising electrochemical and thermal stability.
abstract: Novel ter(9,9-diarylfluorene)s were synthesized by a Suzuki-coupling reaction of 2-bromofluorene (1) and 2,7-fluorenediboronic ester derivatives (3) with high isolated yields (63-86%). The X-ray structure analysis of ter(9,9'-spirobifluorene) (4aa) revealed that the conjugated chromophore adopts a helical conformation. This conformation effectively releases the steric interaction between the fluorene moieties and prevents inter-chromophore interactions. The introduction of aryl groups at the C9 position of fluorene was highly beneficial to the thermal and morphological stability of these oligomers. These terfluorenes exhibit intense blue fluorescence with excellent quantum yields both in solution ( approximately 100%) and in solid state (66-90%), and possess interesting reversible redox properties. Highly efficient blue light-emitting OLED devices were fabricated using 4aa and 4cc as emitters as well as hole transporters. The devices exhibit low turn-on voltage ( approximately 3 V) and high EL external quantum efficiency (2.5-3%).
authors.affiliation: Department of Chemistry, Graduate Institute of Electro-optical Engineering, National Taiwan University, Taipei 106, Taiwan. kenwong@ccms.ntu.edu.tw
authors.forename: Ken-Tsung
authors.initials: KT
authors.lastname: Wong
authors.forename: Yuh-Yih
authors.initials: YY
authors.lastname: Chien
authors.forename: Ruei-Tang
authors.initials: RT
authors.lastname: Chen
authors.forename: Chung-Feng
authors.initials: CF
authors.lastname: Wang
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Lin
authors.forename: Huo-Hsien
authors.initials: HH
authors.lastname: Chiang
authors.forename: Ping-Yuan
authors.initials: PY
authors.lastname: Hsieh
authors.forename: Chung-Chih
authors.initials: CC
authors.lastname: Wu
authors.forename: Chung Hsien
authors.initials: CH
authors.lastname: Chou
authors.forename: Yuhlong Oliver
authors.initials: YO
authors.lastname: Su
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Shie-Ming
authors.initials: SM
authors.lastname: Peng