Impedance spectroscopy of single- and double-layer polymer light-emitting diode

ac electrical properties of the heterostructured polymer light-emitting diode consisting of poly[2-methoxy-5-(2 prime -ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and sodium sulfonated polystyrene (SSPS) ionomer are studied. It is found that the carrier in SSPS is not the ion but the electron, and the conduction mechanism seems to be a space-charge limited current with exponential trap distribution. Based on the results of the impedance analysis, we propose a microscopic model to explain the enhancement of the electroluminescence efficiency of the indium tin oxide/MEH-PPV/SSPS/AI structure. © 2000 American Institute of Physics.