Cationic effects in polymer light-emitting electrochemical cells

The authors show that the emission zone position in a polymer light-emitting electrochemical cell (LEC) can be dramatically shifted by varying the monovalent cations used in the polymer electrolyte. A narrow light-emitting p-n junction very close to the center of the device has been imaged in planar LECs made with rubidium or cesium perchlorate, as compared to a more off-centered emission zone observed in LECs using other alkali perchlorates. In addition, LECs with a more centered emission zone display higher electroluminescence efficiency and better current stability. The authors attribute this effect to that of the cation size and mass, which affects the ionic mobility and doping propagation speed.