Research group of Thuc-Quen Nguen at UC Santa Barbara has published a study aimed to design anionic conjugated polyelectrolyte (CPE) that could enable improved temporal response through facilitation of ion motion. Such an improvement would be greatly beneficial for the development of better PLEDs based displays. They had designed their polyelectrolyte to contain ion-conducting polyethylene oxide pendant (PFPEOCO2Na) as electron injection layers (EILs). Pristine PLEDs containing PFPEOCO2Na exhibit luminance response times on the order of tenths of seconds. This delay is attributed to the formation of ordered structures within the CPE film that slow ion migration and therefore result in a longer temporal response time. The researchers have found out that presence of the ethylene oxide units on PFPEOCO2Na did not improve the luminance response times of as cast PLEDs (46s). Yet it is possible to accelerate the response by a combination of thermal and voltage treatments that “lock” ions within the interfaces adjacent to PFPEOCO2Na resulting in the response time of 200 micro seconds (105 fold enhancement). This study may lead to the development of efficient multilayer solution-processable PLEDs with stable high work function cathodes and fast luminance response time.
Original article is published by the Journal of American Chemical Society DOI 10.1021/ja106268w