Browsing by Author "Wu, Tang-Iy"

Now showing 1 - 2 of 2

A novel fluorene-triphenylamine hybrid that is a highly efficient host material for blue-, green-, and red-light-emitting electrophosphorescent devices
(2007-11-23)
Shih, Ping-I
;
Chien, Chen-Han
;
Wu, Tang-Iy
;
Shu, Ching-Fong
;
應用化學系
TFTPA (tris[4-(9-phenylfluoren-9-yl)phenyl]amine), a novel host material that contains a triphenylamine core and three 9-phenyl-9-fluorenyl peripheries, was effectively synthesized through a Friedel-Crafts-type substitution reaction. Owing to the presence of its sterically bulky 9-phenyl-9-fluorenyl groups, TFTPA exhibits a high glass transition temperature (186 degrees C) and is morphologically and electrochemically stable. In addition, as demonstrated from atomic force microscopy measurements, the aggregation of the triplet iridium dopant is significantly diminished in the TFTPA host, resulting in a highly efficient full-color phosphorescence. The performance of TFTPA-based devices is far superior to those of the corresponding mCP- or CBP-based devices, particularly in blue- and red-emitting electrophosphorescent device systems. The efficiency of the FIrpic-based blue-emitting device reached 12% (26 cd A(-1)) and 18 lm W-1 at a practical brightness of 100 cd m(-2); the Ir(piq)(2)acac-based red-emitting device exhibited an extremely low turn-on voltage (2.6 V) and a threefold enhancement in device efficiency (9.0 lm W-1) relative to those of reference devices based on the CBP host material.
Orange and red organic light-emitting devices employing neutral Ru(II) emitters: Rational design and prospects for color tuning
(2006-08-04)
Tung, Yung-Liang
;
Chen, Li-Shiuan
;
Chi, Yun
;
Chou, Pi-Tai
;
Cheng, Yi-Ming
A new series of charge-neutral Ru(II) pyridyl and isoquinoline pyrazolate complexes, [Ru(bppz)(2)(PPh2Me)(2)] (bbpz: 3-tert-butyl-5-pyridyl pyrazolate) (1), [Ru(fppz)(2)(PPh2Me)(2)] (fppz: 3-trifluoromethyl-5-pyridyl pyrazolate) (2), [Ru(ibpz)(2)(PPhMe2)(2)] (ibpz: 3-tert-butyl-5-(1-isoquinolyl) pyrazolate) (3), [Ru(ibpz)(2)(PPh2Me)(2)] (4), [Ru(ifpz)(2)(PPh2Me)(2)] (ifpz: 3-trifluoromethyl-5-(1-isoquinolyl) pyrazolate) (5), [Ru(ibpz)(2)(dpp=)] (dpp= represents cis-1,2-bis-(diphenylphosphino)ethene) (6), and [Ru(ifpz)(2)(dpp=)] (7), have been synthesized, and their structural, electrochemical, and photophysical properties have been characterized. A comprehensive time-dependant density functional theory (TDDFT) approach has been used to assign the observed electronic transitions to specific frontier orbital configurations. A multilayer organic light-emitting device (OLED) using 24 wt % of 5 as the dopant emitter in a 4,4'-N,N'-dicarbazolyl-1,1'-biphenyl (CBP) host with 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) as the hole-transport layer exhibits saturated red emission with an external quantum efficiency (EQE) of 5.10%, luminous efficiency of 5.74 cd A(-1), and power efficiency of 2.62 lm W-1. The incorporation of a thin layer of poly(styrene sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT) between indium tin oxide (ITO) and NPB gave anoptimized device with an EQE of 7.03%, luminous efficiency of 8.02 cd A(-1), and power efficiency of 2.74 lm W-1 at 20 mA cm(-2). These values represent a breakthrough in the field of OLEDs using less expensive Ru(II) metal complexes. The nonionic nature of the complexes as well as their high emission quantum efficiencies and short radiative lifetimes are believed to be the key factors enabling this unprecedented achievement. The prospects for color tuning based on Ru(II) complexes are also discussed in light of some theoretical calculations.