Browsing by Author "Chiang, CL"

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Improved synthesis of 2,2'-dibromo-9,9'-spirobifluorene and its 2,2'-bisdonor-7,7'-bisacceptor-substituted fluorescent derivatives
(2005-08-18)
Chiang, CL
;
Shu, CF
;
Chen, CT
;
應用化學系
;
Department of Applied Chemistry
[graphics] Pure 2,2'-Dibromo-9,9'-spirobifluorene was synthesized by a method that did not involve troublesome dibromination of 9,9'-spirobifluorene or Sandmeyer reaction of 2,2'-diamino-9,9'-spirobifluorene. A series of donor-acceptor orthogonally substituted 9,9'-spirobifluorene was subsequently prepared showing rich variation of fluorescence in solution and in solid state.
Red fluorenes as the efficient host emitter for non-doped red organic light-emitting diodes
(2005-01-01)
Chiang, CL
;
Wu, MF
;
Shu, CF
;
Chen, CT
;
應用化學系
Crystallinic red fluorophores based on donor-acceptor substituted spirofluorene, i.e., PhSPDCV show strong fluorescence in solution (Phi(f) - 70%) as well as in solid state (Phi(f) > 30 %). Non-doped red OLEDs fabricated with PhSPDCV exhibit authentic red (CIE, x = 0.65, y = 0.35) electroluminescence with brightness over 12,000 cd m(-2) (or > 600 cd m(-2) at 20 mA cm(-2)) and remarkable external quantum efficiency as high as 3.6%. On the other hand, the bis-substituted derivatives of spirofluorene BisPhSPDCV show relatively weak fluorescence both in solution (Phi(f) < 20 %) and in solid state (Phi(f) < 10 %). Although saturated red electroluminescence (CIE, x = 0.65, y = 0.34) is also observed, non-doped red OLED containing BisPhSPDCV performs much worse than PhSPDCV OLEDs. Both PhSPDCV and BisPhSPDCV are not amorphous forming loosely packed crystallinic materials in solid state with no intimate pi-pi interaction.
Synthesis and characterization of new polyquinolines containing 9,9 '-spirobifluorene units
(2002-02-01)
Chiang, CL
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
Polyquinolines, which contain 9,9'-spirobifluorene units in the main chain, were synthesized via the acid-catalyzed Friedlander condensation reactions of bis(o-aminoketone) with bisacetyl monomers. In the spiro-fused bifluorene moiety, the two mutually perpendicular fluorene rings were connected via a common tetracoordinated carbon atom. This structural feature leads to polymers that possess high thermal stability and good solubility in common organic solvents. The polyquinolines have similar lowest energy transitions that can be attributed to a pi-pi* transition with lambda(max) values in the 363-385 nm range and exhibit blue emission. A model compound was synthesized to demonstrate that the tetrahedral bonding carbon at the center of the spiro moiety could serve as a conjugation interrupt to effectively control the conjugation length of the polymers. The electrochemical behaviors of these polymers were investigated by cyclic voltammetry. The reversible reduction and low-lying LUMO energy level suggest that some of the polyquinolines might have potential for use as materials for electron injection and transport in polymer LEDs.