Planar polymer light-emitting electrochemical cells.

摘要

The Light-emitting Electrochemical Cell (LEC) is a novel, polymer-based light emitting device consisting of a light emitting polymer blended with a polymer electrolyte. In contrast to organic and polymer Light Emitting Diodes (LEDs), the LEC operates on the basis of in-situ electrochemical doping and the formation of a dynamic p-n junction upon application of a voltage bias. The dynamic LEC device can also be made static by reducing the temperature below the glass transition temperature of the electrolyte. The resulting frozen-junction LEC maintains a constant doping profile, even upon removal of the initial bias, and displays many of the beneficial properties of inorganic LEDs. While nearly all prior study of these devices has been in thin, sandwich configuration devices, this study explores the properties of LECs fabricated in a massive planar configuration (pLECs). These devices have interelectrode spacings several orders of magnitude larger than any prior planar devices and provide a unique means to directly study the cross-section of the light emitting device. The electrochemical doping picture of LEC operation, a subject of recent debate, has been directly confirmed using spatially and temporally resolved, high resolution imaging. Further, the cessation of ionic motion is demonstrated and pLEC devices are shown to operate in frozen junction mode at 200K. These frozen pLECs are subsequently used to identify degradation mechanisms intrinsic to the light emitting polymer. Finally, i a summary of current and future work in the field of pLEC research is presented.