Electroluminescence of poly(N-vinylcarbazole) and its blends with poly(4,4'-dialkyl-2,2 '-bithiophene)

Polymer light-emitting diodes (LEDs) have been fabricated from poly(N-vinyl carbazole) (PVK) or from blends of PVK and poly(4,4 ' -dialkyl-2,2 ' -bithi ophene) (PDABT). Since PDABT and PVK are soluble in common organic solvents , thin polymer layers needed for the construction of diodes can be prepared by casting from appropriate solutions using the spin-coating technique. No subsequent processing or heat treatment is required. The active part of th e diode consists of one polymer layer which is sandwiched between two elect rodes, an indium tin oxide (ITO) transparent electrode and an Ca/Al electro de. In order to achieve bipolarity in the single polymer emitter layer, PVK was molecularly mixed with electron transport additives, such as PDABT. Th is approach enabled us to improve the efficiencies of the prepared LEDs. Th e light emission appears at (ca) under bar 7 V with the maximum of the band at 530 nm.