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A Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl‐Substituted Fluorene Units for Highly Efficient Blue Electrophosphorescence
Author(s) -
Hsu FangMing,
Chien ChenHan,
Shu ChingFong,
Lai ChinHung,
Hsieh ChengChih,
Wang KangWei,
Chou PiTai
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200900703
Subject(s) - triphenylamine , electroluminescence , materials science , iridium , fluorene , phosphorescence , oled , photochemistry , optoelectronics , nanotechnology , chemistry , physics , optics , organic chemistry , polymer , fluorescence , layer (electronics) , composite material , catalysis
Highly efficient blue electrophosphorescent organic light‐emitting diodes incorporating a bipolar host, 2,7‐bis(diphenylphosphoryl)‐9‐[4‐( N , N ‐diphenylamino)phenyl]‐9‐phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6‐difluoro‐phenyl)pyridinato‐ N , C 2´ ]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron‐donating (p‐type) triphenylamine group and an electron‐accepting (n‐type) 2,7‐bis(diphenyl‐phosphoryl)fluorene segment linked through the sp 3 ‐hybridized C9 position of the fluorene unit. The lack of conjugation between these p‐ and n‐type groups endows POAPF with a triplet energy gap ( E T ) of 2.75 eV, which is sufficiently high to confine the triplet excitons on the blue‐emitting guest. In addition, the built‐in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF‐based device doped with 7 wt% FIrpic exhibits a very low turn‐on voltage (2.5 V) and high electroluminescence efficiencies (20.6% and 36.7 lm W −1 ). Even at the practical brightnesses of 100 and 1000 cd m −2 , the efficiencies remain high (20.2%/33.8 lm W −1 and 18.8%/24.3 lm W −1 , respectively), making POAPF a promising material for use in low‐power‐consumption devices for next‐generation flat‐panel displays and light sources.