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Synthesis of luminophoric disubstituted polyacetylenes and fabrications of efficient, stable, blue light-emitting diodes

Authors Xie, Zhiliang
Issue Date 2003
Summary New disubstituted polyacetylenes carrying functional groups (FG) -[(C6H13)C=C(C6H4CO2-FG)]n-, -{ (C6H5)C=C[(CH2)m-FG] }n-, and were designed and synthesized. The monomers were prepared in high yields by multi-step reactions. Polymerizations of the monomers were effected by inexpensive classical metathesis catalysts of WCl6- and NbCl5-Ph4Sn, giving high molecular weight polymers in high yields (Mw up to 2.6 x 105 Dalton and isolation yield up to 95%). The structures and properties of the polymers were well characterized and evaluated by IR, NMR, UV, TGA, PL, EL, and CD analyses. All the polymers possessed high thermal stability and they started to lose weights at high temperature up to 440°C. The chromophoric pendants had endowed the polymers with novel optical properties. Upon photoexcitation, the polymers emitted intense blue light with quantum yield up to 96%. Multilayer EL devices with a configuration of ITO/Polymer/BCP/Alq3/LiF/Al were constructed, which emitted blue light in high luminance of 1136 cd/m2 and external quantum efficiency of 0.72%. Optimization of the device configuration further enhanced the performance and the maximum external quantum efficiency could reach 0.86%. The blue EL from a carbazole-containing polyacetylene could be converted into more efficient green or red EL by doping a corresponding phosphorescent dye Ir(ppy)3 or btp2Ir(acac). The btp2Ir(acac)-doping device exhibited pure red EL with maximum external quantum efficiency of 1.73%, which are the best among polyacetylenes attainable so far. The emission color of silole-containing polyacetylenes can be tuned to red, green, and blue-green by molecular engineering endeavors. The PL quantum yield in solid film of monosubstituted polyacetylenes with silole pendants could achieve 32%, which is 320 times higher than the best result reported before. The EL from liquid crystalline polyacetylenes was first studied. No change in the EL spectra was observed in almost all of our substituted polyacetylenes upon increment of voltage, suggestive of their outstanding spectral stability.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2003
Language English
Format Thesis
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