Polymer light-emitting electrochemical cells with frozen junctions

We report on polymer light-emitting electrochemical cells (LECs) with froze n p-i-n junctions. The dynamic 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 p-i-n ju nction in LECs based on the luminescent polymer poly[5-(2'ethylhexyloxy)-2- methoxy-1,4-phenylene vinylene] and polyethylene oxide containing lithium t riflate (PEO:LiCF3SO3) is stable at temperatures up to 200 K. Frozen-juncti on 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. (C) 1999 Amer ican Institute of Physics. [S0021-8979(99)06920-0].