NOVEL BLUE ELECTROLUMINESCENT POLYMERS WITH WELL-DEFINED CONJUGATION LENGTH

Light emission from pale blue to greenish blue is successfully obtained from the diodes made of the trimethylsilyl-, monoalkoxy-, and dialkoxy-substituted polymers with well-defined conjugation length containing phenylenevinylene units. The conjugation length is adjusted by incorporating the nonconjugated spacer group in the backbone. The polymers are organic soluble and allow the fabrication of the light-emitting diode by spinning without further thermal processes. The fabricated devices show typical diode characteristics with operation voltages of 15-20 V, and the light is visible at the current density of about less than 0.5 mA/cm(2) for all three devices. The electroluminescence spectra are similar to the photoluminescence spectra and show the red shift as the electron-donation effects of the substituents become stronger. The bluest color of light emission corresponds to 470 nm for the polymer with trimethylsilyl substituent.