Towards frozen organic PN junctions at room temperature using high-Tg polymeric electrolytes

Light-emitting electrochemical cells (LECs) based on a semiconducting polymer blended with lithium salt and novel polyelectrolytes have been studied. Random copolymers of poly(ethylene glycol) methyl ether methacrylate have been developed in order to increase their glass transition temperature (Tg) above room temperature. Devices have been optimized and successfully turned on upon heating. Cooling devices under applied voltage bias down to room temperature leads to frozen PN junctions. The relaxation of these junctions over voltage-free storage is studied. The higher the Tg, the longer the shelf-life of the junctions. This research opens the route to room temperature stable organic PN junctions for use in organic electronic devices such as light-emitting diodes, photovoltaic solar cells and other organic electronic devices.

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► Random copolymers of poly(ethylene glycol) methyl ether methacrylate were synthesized.
► Polymeric LEC-based PN junctions are turned-on upon heating.
► The PN junction is frozen at room temperature.
► The higher the Tg of the electrolyte, the slower the junction relaxation over time.