Effects of dilution and charge trapping on the performance of a light-emitting diode of poly(9-vinylcarbazole) doped with poly[2-methoxy-5-(20- ethyl hexyloxy)-1,4-phenylene vinylene]

摘要

We report the electroluminescence (EL) enhancement of polymer light-emitting diodes made by the dispersion of poly[2-methoxy-5-(2′-ethyl hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) into poly(9-vinylcarba-zole) (PVK). From the photoluminescence and EL spectra of the polymer blend films, we found that, because of the dilution effect, interchain interactions in MEH-PPV were reduced markedly. The EL spectrum indicated that the charge-trapping effect contributed to the formation of exci-tons at the MEH-PPV centers and, thus, strongly enhanced EL. Because of the balance between increasing trapping centers and suppressing interchain interactions, the best device performance was achieved when the polymer blend contained 12% MEH-PPV and 88% PVK (weight ratio), and this also led to improved color purity of the polymer blend devices