Origin of bistable memory characteristics of organic light-emitting diodes with LiF/Al cathode

Bistable memory performances of organic light-emitting diodes (OLEDs) with LiF/Al cathode were investigated and the origin of bistability was studied. LiF was essential to get stable memory performances in OLEDs and on/off ratio was improved by more than 50 times by using LiF/Al instead of Al cathode. High on/off ratio over 1000 was obtained from switching test and the multilevel switching of organic light-emitting bistable devices (OLEBDs) was realized by changing the writing voltage of OLEBDs. AlF3 formation at the interface during evaporation of Al was proposed as the main mechanism for bistability of OLEBDs.