Dual-layer light emitting devices based on polymeric Langmuir-Blodgett films

Poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) and poly(6-hexylpyridine-2,5-diyl) (PHPY) Langmuir-Blodgett films have been used as emitting layer and electron transporting layer, respectively, in light emitting diodes. The electrical and opto-electrical characteristics of the dual-layer devices have been compared to single layer devices based on MEH-PPV. AC impedance measurements over the frequency range 5 Hz-13 MHz have been used to provide an insight into the electrical equivalent circuit of the devices. The external quantum efficiency of the dual-layer structure was found to be approximately ten times higher than that of the single layer device.