Light-Emitting Devices Based on Electrochemiluminescence: Comparison to Traditional Light-Emitting Electrochemical Cells

Electrochemical processes can be exploited to operate light-emitting devices with unusual functionality. For example, light-emitting electrochemical cells (LECs) contain a small amount of electrolyte within the organic/polymer light-emitting active layer. The electrolyte in the active layer allows the multiple charge injection layers that are deemed critical for organic light-emitting diodes to be avoided. Very recently, an alternative light-emitting device platform based on electrochemical processes was also suggested. These devices rely on electrochemiluminescence (ECL), a light-emission process based on the charge transfer reaction between reduced and oxidized forms of luminophores. Although the ECL process has been extensively investigated in the field of analytical chemistry, its utilization in electronic devices is a new approach that offers unique opportunities. Despite the interesting opportunities, a good introduction to the subject is not available, particularly with a focus on electronic device applications. Moreover, the operation of ECL devices is often confused with that of LECs, even though they follow distinct working principles. This confusion occurs mainly because the active layers for both ECL devices and LECs contain light-emitting material and electrolyte material (although their compositions are completely different). Therefore, clarifying the difference between the two sister devices would be both necessary and useful. In particular, a comparison of the two sister devices would highlight the unique opportunities for ECL devices and inspire researchers to devise a novel light-emitting device platform, which is the primary goal of this perspective.