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A poly(ethylene oxide) (PEO) oligomer capped with methacrylate end groups can conduct ionic species for the formation of p−i−n junction in polymer light-emitting electrochemical cells (LECs). The polymerization of the methacrylate during the junction formation can mitigate the nonuniformity of the doping frontiers and enhance the uniformity and stability of the junction. Sandwich-structured LECs employing this ionic conductor exhibit both high electroluminescent efficiency and stability. Luminous efficiency greater than 15 lm/W has been obtained using a yellow light-emitting poly(1,4-phenylene vinylene) derivative (Super-Yellow by Covion). In accelerated lifetime testing, the brightness dropped to 75% of the maximum 2200 cd/m2 of luminance (T 75%) in 102 h under constant current operation; this corresponds to a lifetime (T 75%) of 27 000 h at 100 cd/m2 of peak brightness. Both the efficiency and lifetime are comparable to the best-performing polymer OLEDs optimized for commercial applications.

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