Synthesis and electroluminescent property of a new conjugated polymer based on carbazole derivative: poly (3,6-N-2-ethylhexyl carbazolyl cyanoterephthalidene)

A new green electroluminescence polymer, poly (3,6-N-2-ethylhexyl carbazolyl cyanoterephthalidene), was synthesized by condensation polymerization employing the Knoevenagel reaction. The resulting polymer has relatively high molecular weight (Mn = 3.7×104), exhibits good solubility in common organic solvents such as chloroform, THF, etc., and has good stability in air. This polymer is also easily cast on glass plate to give yellow-colored film. The structure of the resulting polymer was identified by 1H, 13C NMR, FT-IR and UV-Vis spectroscopies. The UV-Vis spectrum of the polymer in chloroform exhibits characteristically a broad absorption band at 360–500 nm which is due to the π-π* transition of the conjugated double bond. This polymer shows photoluminescence around λmax = 525 nm (exciting wavelength, 410 nm) and green electroluminescence around λmax = 510 nm. The current-voltage (I-V) curve of the polymer shows typical rectifying diode characteristics in the Al/polymer/ITO device.