Effect of electron- and hole-transporting materials on the performance of FIrpic-doped PVK phosphorescent devices

PVK-based phosphorescent FIrpic-doped devices have been fabricated and the effect of carrier transporting materials on the device performance has been investigated. We have fabricated the single-layer and double-layer devices to investigate the role of electron- and hole-transporting materials both when they are mixed in the single- and separated from the emissive layer. We have studied NPB as a hole-transporting material, OXD-7 and PBD as electron-transporting materials. Even though PBD had been well known to be unsuitable as an electron-transporting material for FIrpic-doped PVK devices, it was found in this study that the separate utilization of PBD from PVK:FIrpic layer instead of mixing it with the emissive layer could enhance the device performance significantly. Nevertheless, the OXD-7 was found not only superior to PBD as the electron-transporting material for FIrpic-doped PVK devices but also suitable as an electron-transporting material for the single-layer devices.