Light emission at 5V from a polymer device with a millimeter-sized interelectrode gap

Abstract

We report the onset of electrochemical doping and subsequent visible light emission at 5V and 360K from a planar light-emitting electrochemical cell with a 1mm interelectrode gap containing poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), poly(ethylene oxide) (PEO), and XCF3SO3 (X=K,Li) as the active material. We rationalize the unprecedented low turn-on voltage of such wide-gap light-emitting electrochemical cells by demonstrating that the active material contains a mixture of crystalline PEO+XCF3SO3 domains and amorphous MEH-PPV domains at room temperature, but that the crystalline domains have melted at 360K resulting in a significant increase in the ionic conductivity.