Phenylene-functionalized polythiophene derivatives for light-emitting diodes: Their synthesis, characterization and properties

The design, synthesis and characterization of a new series of conjugated polymers, poly[(3-(4′-n-butylphenyl)thiophene-2,5-diyl)(2,5-dialkoxy-1,4- phenylene)(4-(4′-n-butylphenyl)thiophene-2,5-diyl)] are described in this contribution. Three polymers modified by phenyl groups have been successfully synthesized via FeCl₃-oxiditive polymerization. The well-defined structure of the polymers is fully verified by elemental analysis, FT-IR, and ¹H and ¹³C NMR spectroscopy. All polymers show good thermal stability and solubility in common organic solvents. The absolute photoluminescence (PL) efficiencies of the polymers in the neat film can be up to 11%. The electrochemical properties of the polymers indicate that their HOMO and LUMO energy levels can be adjusted by means of the aromatic groups both in the side chain and the backbone structure. Yellowish green electroluminescence is achieved from single-layered polymer light-emitting diodes (PLEDs) with the configuration ITO/polymer/Ca or Al.