Browsing by Author "Chuang, Chu-Ying"

Now showing 1 - 3 of 3

Bright-white light-emitting devices based on a single polymer exhibiting simultaneous blue, green, and red emissions
(2007-01-23)
Chuang, Chu-Ying
;
Shih, Ping-I
;
Chien, Chen-Han
;
Wu, Fang-Iy
;
Shu, Ching-Fong
We have developed efficient white-light-emitting polymers through the incorporation of low band gap green-light-emitting benzothiadiazole and red-light-emitting bisthiophenylbenzothiadiazole moieties into the backbone of a blue-light-emitting bipolar polyfluorene copolymer. Partial energy transfer from the blue-fluorescent polyfluorene backbone to the green- and red-fluorescent components resulted in individual emissions from the three emissive species. By carefully controlling the concentrations of the low-energy-emitting species in the resulting copolymers, the emission of white light, with contributions from each of the three primary colors, was achieved. Efficient polymer light-emitting devices prepared using these copolymers exhibited luminance efficiencies as high as 4.87 cd/A with color coordinates (0.37, 0.36) that were very close to the ideal CIE chromaticity coordinates for pure white light (0.33, 0.33). In addition, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study suggested that energy transfer from the fluorene segments to the low band gap units, rather than charge trapping, was the main operating process involved in the electroluminescent process.
Highly efficient non-doped blue-light-emitting diodes based on an anthrancene derivative end-capped with tetraphenylethylene groups
(2007-11-05)
Shih, Ping-I
;
Chuang, Chu-Ying
;
Chien, Chen-Han
;
Diau, Eric Wei-Guang
;
Shu, Ching-Fong
A novel blue-emitting material, 2-tert-butyl-9,10-bis[4-(1,2,2-triphenylvinyl)phenyl]anthracene (TPVAn), which contains an anthracene core and two tetraphenylethylene end-capped groups, has been synthesized and characterized. Owing to the presence of its sterically congested terminal groups, TPVAn possesses a high glass transition temperature (155 degrees C) and is morphologically stable. Organic light-emitting diodes (OLEDs) utilizing TPVAn as the emitter exhibit bright saturated-blue emissions (Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of x = 0.14 and y = 0.12) with efficiencies as high as 5.3% (5.3 cd A(-1)) - the best performance of non-doped deep blue-emitting OLEDs reported to date. In addition, TPVAn doped with an orange fluorophore served as an authentic host for the construction of a white-light-emitting device that displayed promising electroluminescent characteristics: the maximum external quantum efficiency reached 4.9% (13.1 cd A(-1)) with CIE coordinates located at (0.33, 0.39).
Novel host material for highly efficient blue phosphorescent OLEDs
(2007)
Shih, Ping-I
;
Chien, Chen-Han
;
Chuang, Chu-Ying
;
Shu, Ching-Fong
;
Yang, Cheng-Han
We report the synthesis and characterization of a novel silane - fluorene hybrid, triphenyl-(4-(9-phenyl- 9H-fluoren-9-yl) phenyl) silane (TPSi-F), used as the host material for blue phosphorescent devices. TPSi-F is constructed by linking p-substituted tetraphenylsilane to the fluorene framework through a non-conjugated, sp(3)-hybridized carbon atom (C- 9) to enhance thermal and morphological stabilities, while maintaining the much needed higher singlet and triplet energy gap. Highly efficient sky-blue phosphorescent OLEDs were obtained when employing TPSi-F as the host and iridium(III) bis[(4,6-difluorophenyl) pyridinato-N,C-2'] (FIrpic) as the guest. The maximum external quantum efficiency (max. E. Q. E.) of this device reached as high as 15% (30.6 cd A(-1)). Furthermore, upon switching the guest from FIrpic to a new blue phosphor FIrfpy, better blue-emitting OLEDs were produced with a max. E. Q. E. of 9.4% (15.1 cd A(-1)). These TPSi-F based blue phosphorescent devices show a 2-fold enhancement in device efficiency compared with reference devices based on the conventional host material 1,3-bis(9-carbazolyl) benzene (mCP).