ELECTROLUMINESCENCE FROM BLEND FILMS OF POLY(3-HEXYLTHIOPHENE) AND POLY(N-VINYLCARBAZOLE)

Electroluminescence (EL) is reported from blends of head-to-tail poly(3-hexylthiophene) (P3HT) and poly(N-vinylcarbazole) (PVK); light-violet color emission is observed (a mixture of blue and red). Since P3HT and PVK are soluble in common organic solvents, light-emitting diodes (LEDs) can be fabricated by spin-casting films of the polymer blends from solution without subsequent processing or heat treatment. Calcium and indium-tin oxide (ITO) were used as the electron-injection and hole-injection electrodes, respectively. The EL quantum efficiency was enhanced by blending, with an optimized value of 0.2% photons/electron in blend films with about 2 wt.% P3HT; i.e. greater than in pure PVK by approximately a factor of four and greater than in pure P3HT by more than two orders of magnitude.