Polymer light-emitting electrochemical cells with frozen junctions

We report on polymer light-emitting electrochemical cells (LECs) with frozen $\mathrm{p-i-n}$ junctions. The dynamic $\mathrm{p-i-n}$ junction in polymer LECs is stabilized by lowering the temperature below the glass transition temperature of the ion-transport polymer. Detailed studies have shown that the frozen $\mathrm{p-i-n}$ junction in LECs based on the luminescent polymer poly[5-(2^′ethylhexyloxy)-2-methoxy-1,4-phenylene vinylene] and polyethylene oxide containing lithium triflate $({\mathrm{PEO:LiCF}}_{\mathrm{3}}{\mathrm{SO}}_{\mathrm{3}})$ is stable at temperatures up to 200 K. Frozen-junction LECs offer a number of advantages; they exhibit unipolar light emission, balanced injection, fast response, high brightness, low operating voltage, and insensitivity to electrode materials and film thickness.