Synthesis and characterization of novel light-emitting copolymers with electron-withdrawing substituents
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We synthesized two new series of alternating copolymers, poly[bis(2-(4-phenylenevinylene)-2-cyanoethenyl)-9,9-dihexyl-9H-fluoren-2,7-yl-alt-1,4-phenylene](Polymer-I) and poly[bis(2-(4-phenylenevinylene)-2-cyanoethenyl)-9,9-dihexyl-9H-fluoren-2,7-yl-alt-2,7-(9,9-dihexylfluorene)](Polymer-II), via the Suzuki coupling reaction, for use in light-emitting diodes(LEDs). Defect-free uniformly thin films of these polymers were found to be easily formed on indium-tin oxide(ITO) coated glass substrates. Multi-layer LEDs with ITO/PEDOT/Polymer/ LiF/Al configurations with or without an Alq3 electron transport layer were fabricated with these polymers. The maximum EL emissions of Polymer-I and Polymer-II with an Alq3/LiF/Al cathode were observed at 516 and 533 nm, respectively. The maximum brightness and external luminance efficiency of the devices fabricated with the EL polymers were found to be 411 cd/m2 and 0.16 cd/A, respectively.
Keywordselectroluminescence light-emitting polymer light-emitting diode luminescence efficiency
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