Ter(9,9-diarylfluorene)s: highly efficient blue emitter with promising electrochemical and thermal stability.
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%).
Wong
Ken-Tsung
KT
Department of Chemistry, Graduate Institute of Electro-optical Engineering, National Taiwan University, Taipei 106, Taiwan. kenwong@ccms.ntu.edu.tw
Chien
Yuh-Yih
YY
Chen
Ruei-Tang
RT
Wang
Chung-Feng
CF
Lin
Yu-Ting
YT
Chiang
Huo-Hsien
HH
Hsieh
Ping-Yuan
PY
Wu
Chung-Chih
CC
Chou
Chung Hsien
CH
Su
Yuhlong Oliver
YO
Lee
Gene-Hsiang
GH
Peng
Shie-Ming
SM