LIGHT-EMITTING DEVICES BASED ON SOLID ELECTROLYTES AND POLYELECTROLYTES

The properties of light-emitting diodes (LEDs) based on organic layers containing mobile ions, so-called light-emitting electrochemical cell s (LECs), are reviewed. These devices hai le some unique properties: t heir current-voltage characteristics are antisymmetric with respect to the origin and they emit light under both forward and reverse bias. T he physical processes involved in the emission from LECs are discussed in terms of a thermodynamic model. Recent work on blends of luminesce nt and ion-conducting polymers is summarized. In addition, the propert ies of novel single-component LECs and polyelectrolyte-based devices a re presented. The results show that LECs with performances superior to that of conventional LED devices can be fabricated, but questions con cerning the transient behavior and degradation mechanisms persist. (C) 1998 John Wiley These Sons, Ltd.