Browsing by Author "Neher, Dieter"

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Efficient red-emitting electrophosphorescent polymers
(2008-02-26)
Yang, Xiao-Hui
;
Wu, Fang-Iy
;
Neher, Dieter
;
Chien, Chen-Han
;
Shu, Ching-Fong
We report the synthesis and characterization of a series of electrophosphorescent polymers with a polyfluorene backbone, containing a red-emitting iridium complex and carrier-transporting units as the substitutes of the C-9 position of fluorene. Different specimens and contents of the hole-transporting moieties were found to influence the electroluminescent properties of the polymers. Incorporation of a hole-transporting/electron-blocking interfacial layer and utilization of an efficient electron injection cathode led to the saturated red-emitting electrophosphorescent polymer devices with the peak luminance efficiency and power conversion efficiency of 9.3 cd A(-1) and 10.5 lm W-1, respectively. The efficiencies were 8 cd A(-1)/8 lm W-1 and 5.9 cd A(-1)/4.6 lm W-1, respectively, at 100 and 1000 cd m(-2).
Efficient white-electrophosphorescent devices based on a single polyfluorene copolymer
(2007-05-07)
Wu, Fang-Iy
;
Yang, Xiao-Hui
;
Neher, Dieter
;
Dodda, Rajasekhar
;
Tseng, Ya-Hsien
An efficient white-light-emitting polymer (W3) is realized by covalently attaching a green fluorophore and a red phosphor into the backbone and the side chains, respectively, of polyfluorene at a concentration of 0.04 mol %. In addition, charge-transporting pendant units are included to improve carrier injection and transport. White-electrophosphorescent devices with the structure ITO/PEDOT.PSSiW3/CsF/Al (ITO: indium tin oxide; PEDOT.PSS: poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene)) exhibit a low turn-on voltage of 2.8 V and a luminance of ca. 10(3) cd m(-2) at below 6 V. The peak luminance and power-conversion efficiencies are 8.2 cd A(-1) and 7.2 lm W-1, respectively. Furthermore, the device shows relatively stable white emission: the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of the devices change only slightly from (0.35,0.38) at 10 mA cm(-2) to (0.33,0.36) at 100 mA cm(-2), with an almost constant color render index (CRI) value of 82 at all measured current densities.