Electroluminescence and electron transport characteristics of aromatic polyimides containing 1,3,4-oxadiazole moiety

Single and double layer polymer light-emitting diodes (LEDs) were fabricated by using 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO)-based aromatic polyimides (APIs). All the resultant APIs have high glass transition temperatures (Tg > 250 °C) and high thermal decomposition temperatures (Td > 510 °C). The APIs exhibit broad fluorescent characteristic, and the fluorescent intensity is related to the intermolecular chain's orientation. BAO-3,3′-oxydiphthalic anhydride (ODPA) and BAO-4,4′-(hexafluoro-iso-propylidene) diphthalic anhydride show electroluminescent property in single layer LED devices. By inserting BAO-ODPA in the poly(p-phenylene vinylene)-poly(vinylalcohol) LED device to form a double layer device, the EL efficiency can be improved by two orders of magnitude.