We investigate the electrical properties of Polymer Light Emitting Diodes (LED's). The experimental data consists of steady state current-voltage characteristics and radiance as a function of temperature. The basic LED structure is Anode/MEH-PPV (2-methoxy,5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene)/Cathode, with a polymer film 120-140 nm thick. We use different anode/cathode pairs to study transport and light emission properties. Measurements of external quantum efficiency of bipolar and monopolar devices are presented from 200 K to 300 K. The electron and hole mobilities are derived in the trap-free limit and at high voltages
