The composition effect of triphenylamine/polyimide composite nanolayers on the performance of hybrid organic light-emitting devices
Here we report the composition effect of hole-transporting material (HTM)/polyimide (PI) composite nanolayers on the performance of hybrid organic light-emitting devices (OLEDs). A well-established triphenylamine derivative, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-diphenyl]-4,4'-diamine (TPD), was employed as a HTM, while poly(oxydianiline pyromellitimide) (PMDA-ODA PI) was used as a PI component. The composition of TPD in the TPD/PI composite nanolayers was varied between 0 and 70 wt% to fabricate hybrid OLEDs. The results showed that the light-emitting voltage (luminous efficiency) gradually lowered (increased) as the TPD content increased, which was assigned to the improved charge transport with increasing TPD content. However, the trend in device performance was a bit different in the case of 70 wt% TPD content owing to the inversion between the host and the guest. The space-charge-limited current model fitting suggested that the charge transport characteristics of the devices had already begun to change at the TPD content of 30 wt%.