Application of aluminum, copper and gold electrodes in a.c. polymer light-emitting devices

Symmetrically configured a.c. light-emitting (SCALE) ‘5-layer’ devices having the configuration M/EB/P/EB/ITO, where M = Al, Cu or Au, EB = polyaniline (emeraldine base), P = poly(2,5-dihexadecanoxy phenylene vinylene pyridyl vinylene) or PPV-PPyV, and ITO = indium-tin oxide glass, show electroluminescent properties in both forward and reverse bias modes. In the absence of emeraldine base, in the case of aluminum and copper, electroluminescence is observed only in the forward biasmode; in the case of gold no electroluminescence is observed in either forward or reverse bias modes. The electrical properties of the ‘5-layer’ devices (M = Al, Cu) are most surprising since their total resistance at a given applied voltage is significantly less than that of the corresponding devices in which the two polyaniline insulator layers are not present.