Evaluation of Reliability in Rubrene-Based Organic Light Emitting Devices with a Mixed Single Layer

Electrical and emission properties and reliability of organic light emitting device with a mixed single-layer using rubrene as dopant were investigated. Comparing to a conventional heterostructure device, a mixed single-layer device exhibit lower current density in current vs voltage characteristics, however, exhibit equal luminance vs current density characteristics. Particularly, an operational lifetime in the mixed single-layer device was improved by a factor of more than 1.5 compared to the heterostructure device. The improvements of reliability was attributed to the stability in mixing of organic molecule even in higher operational voltage and N , N '-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) as hole transport material. Another possible reason was removal of the heterojunction interface in the mixed single layer device which was resulted in the decrease of electric field. It was confirmed that growth area of dark spot after measuring of half lifetime was decreased.