Circumventing Dedicated Electrolytes in Light-Emitting Electrochemical Cells

Light-emitting electrochemical cells (LECs) are devices that utilize efficient ion redistribution to produce high-efficiency electroluminescence in a simple device architecture. Prototypical polymer LECs utilize three components in the active layer: a luminescent conducting polymer, a salt, and an electrolyte. Similarly, many small-molecule LECs also utilize an electrolyte to disperse salts. In these systems, the electrolyte is incorporated to efficiently conduct ions and to maintain phase compatibility between all components. However, certain LEC approaches and materials systems enable device operation without a dedicated electrolyte. This review describes the general methods and materials used to circumvent the use of a dedicated electrolyte in LECs. The techniques of synthetically coupling electrolytes, incorporating ionic liquids, and introducing inorganic salts are presented in view of research efforts to date. The use of these techniques in emerging classes of light-emitting electrochemical cells is also discussed. These approaches have yielded some of the most efficient, long-lasting, and commercially applicable LECs to date.