Effect of different processing methods for the hole transporting layer on the performance of double layer organic light-emitting devices

TN383+.1; The hole transporting layer (HTL) of organic light-emitting device (OLED) was processed by vacuum deposition and spin coating method, respectively, where N,N'-biphenyl-N, N'-bis(3-methylphenyl)-1, 1'-biphenyl-4,4' -diamine (TPD) and poly (vinylcarbazole) (PVK) acted as the hole-transport materials. Tris-(8-hydroxyquinoline)- aluminum (Alq3) was utilized as both the light-emitting layer and the electron transporting layer. The basic structure of the device cell was: indium-tin-oxide (ITO)/PVK: TPD/Alq3/Mg:Ag. The electroluminescent (EL) characteristics of devices were characterized. The results showed that the peak of EL spectra was located at 530 nm, which conformed to the characterizing spectrum of Alq3.Compared with using vacuum deposition method, the green emission with a maximum luminance up to 26135 cd/m2 could be achieved at a drive voltage of 15 V by selecting proper solvent using spin-coating technique, and its maximum luminance efficiency was 2.56 lm/W at a drive voltage of 5.5 V.