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Cyclic voltammetry (CV) has been performed on light-emitting electrochemical cells (LECs) using poly(3-octylthiophene) (P3OT) as the active luminescent polymer. Above the threshold voltage, current in an LEC consists of ionic and electronic components. A purely ionic (negative) component is clearly discernible in the return scan of the CV below threshold when, as a result of the relaxation of the p-n junction, the electronic current becomes negligible. Analysis of the peak negative current reveals that LECs exhibit a mixture of thin film and diffusion controlled current behavior. Weak orange light emission is observed with an onset above 2 V.

Cyclic voltammetry (CV) studies have been carried out on polymer light-emitting electrochemical cells (LECs) using poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene), MEH-PPV, as the active luminescent polymer. As a result of the slow ionic motion in response to changes in the applied voltage, the CV scans show hysteresis. The onset of electronic current in an LEC is coincident with the onset of electrochemical doping and the formation of a p-n junction. From analysis of the measured current and light emission during cyclic voltammetry, we conclude that the voltage threshold for the onset of electrochemical doping in MEH-PPV is approximately 2.2 V.