Polymer light-emitting diodes (LEDs) have been fabricated from poly(N-vinylcarbazole) (PVK) or from blends of PVK and poly(4,4 ' -dialkyl-2,2 ' -bithiophene) (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 the diode consists of one polymer layer which is sandwiched between two electrodes, an indium tin oxide (ITO) transparent electrode and an Ca/Al electrode. In order to achieve bipolarity in the single polymer emitter layer, PVK was molecularly mixed with electron transport additives, such as PDABT. This approach enabled us to improve the efficiencies of the prepared LEDs. The light emission appears at (ca) under bar 7 V with the maximum of the band at 530 nm.