About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
Polymers for Advanced Technologies
Paper
Heterolayer light-emitting diodes based on poly-phenylene vinylene
Abstract
In order to enhance the quantum efficiency of poly-p-phenylene vinylene (PPV) light-emitting diodes (LEDs), we have fabricated metal/insulator/polymer (MIP) LEDs and heterolayer LEDs based on PPV and oxadiazole polymers. The current-voltage (I-V) characteristics and electroluminescence (EL) intensity of the MIP structures display a pronounced dependence of the insulator thickness and we detect an increase in the quantum efficiency of more than a factor of 30 at an AlOx layer thickness of 3-6 nm. The device characteristics are qualitatively understood within inorganic metal insulator semi-conductor (MIS) theory and can be explained by a voltage-dependent barrier for minority carrier injection in connection with a hole-blocking barrier at the PPV/insulator interface. Our oxadiazole polymers used in the heterolayer polymeric devices are characterized by a high thermal stability and excellent film-forming properties. These materials act as efficient hole-blocking, electron transport and injection layers in PPV-based LEDs and we measure a significantly improved device performance with external quantum efficiencies of more than 0.5%. Temperature-dependent investigations point to a relatively balanced charge carrier injection and reveal the influence of space charge limited currents on the device performance at low temperature. © 1997 by John Wiley & Sons, Ltd.