| Abstract
| - Multi-H shaped macrocyclics have been synthesized for use as blue-light hole-transporting emitters, in which three triphenylamine units are connected in series through C-9's of the central fluorene units of three oligofluorenes to form the macrocyclic core. This specific structure offers the mocrocyclics outstanding photoluminescence stabilities and optoelectronic properties.
- Novel multi-H shaped macrocyclic oligomers ((TPAF3)3 and (TPAF5)3) were designed and synthesizedfor use as hole-transporting emitters in blue-light-emitting diodes (LEDs). In the produced macrocyclics,three triphenylamine units are connected in series to form a macrocyclic core through the C-9's of thecentral fluorene units of three surrounding oligofluorenes, which, like rigid rods, stick out of the ringplane in both sides. This specific structure renders the macrocyclics better photoluminescence (PL)stabilities and lower crystallization tendencies than polyfluorenes and excellent optoelectronic properties.The macrocyclics emit deep blue fluorescence with high efficiencies both in solutions and thin films (Φpl-film = 57% for (TPAF3)3 and 52% for (TPAF5)3). (TPAF5)3 films are stable against both electrochemicaloxidation and reduction, with CV curves remaining unchanged in 10 successive potential scans. High-efficiency blue-light-emitting diodes were fabricated using the macrocyclics as the hole-transportingemitting layer. The device structure used in this study is ITO/(TPAF3)3 or (TPAF5)3)/TPBI//LiF/Al, whereTPBI, 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene, is a morphologically stable material functioningas a hole-blocking/electron-transporting layer. The (TPAF5)3-based devices displayed a low turn-on voltageof 4 V and a maximum luminance of 1716 cd/m2 at a voltage of 14.1 V; the (TPAF3)3-based devicesgave 901 cd/m2 at 13.0 V. The maximum luminous efficiencies of the (TPAF3)3- and (TPAF5)3-baseddevices reached 0.63 cd/A at 187 cd/m2 and 0.93 cd/A at 340 cd/m2, respectively.
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