SYNTHESIS AND ELECTROLUMINESCENCE STUDY OF A NOVEL COPOLYMER : POLY(PHENYLENE VINYLENE-CO-QUINOLINE VINYLENE)

摘要

High-efficiency polymer light-emitting diodes (LEDs) are often fabricated using multi-layered structures with separate carrier transport and light emission layers. Recently, we reported on the synthesis and electroluminescence (EL) characteristics of poly(2,6-quinoline vinylene) (PQV) and its potential for use as an electron transport layer in poly(phenylene vinylene) (PPV) LEDs. To take advantage of the high emission efficiency of PPV and electron accepting ability of PQV, a copolymer of PPV and PQV, poly(phenylene vinylene-co-quinoline vinylene) (PPVQV) was synthesized via the precursor polymer route and converted to the conjugated form by thermal elimination. When used as the emissive layer with Indium-Tin Oxide (ITO) and aluminum as positive and negative electrodes respectively, PPVQV emitted blue light at an onset electric field of 1.05 × 10~6 V/cm and emission efficiency of 0.08%. Improved efficiencies of the order of 0.15% were obtained when blends of copolymer with PPV were used in conjunction with PPV in a multi-layered structure. Along with copolymer chemical characterization data, results from EL studies on single and multi-layered devices are discussed. We also report on a simple and cost-effective chemical deposition of silver for the negative electrode in polymer LEDs.