Light-emitting electrochemical cells with crown ether as solid electrolyte

Light-emitting electrochemical cells (LECs) are reported with lithium salt/crown ether complex as the solid electrolyte. By careful choice of the combination of electroluminescent polymer, crown ether, and lithium salt, LECs are demonstrated with good quantum efficiency, fast response, and long stress life. The results demonstrate the importance of phase compatibility to LEC performance. Pei et al. ' described a light-emitting device using solid-state electrochemical cells in which a blend of conjugated luminescent polymer and solid electrolyte serves as the active layer. The oper-ating mechanism proposed for the polymer LEC involves the fol-lowing steps: (i) electrochemical p- and n-doping in the regions adjacent to anode and cathode, respectively, on application of volt-age greater than Eg/e where E, is the T- 7 * energy gap of the semi-conducting polymer and e is the electronic charge; (ii) formation in situ of a p-i-n junction within the active layer; and (iii) radiative recombination of p- and n-type carriers within the compensated (i) region of the p-i-n junction. Based on this mechanism, it is obviou