Investigation of organic light-emitting diodes with novel organic electron injection layers

1-(diphenyl-phosphinoyl)-4-(2,2-diphenyl-vinyl)-benzene (DpDvB) and 4-(diphenyl-phosphinoyl)-4′-(2,2-diphenyl-vinyl)-biphenyl (DpDvBp) have been prepared and used as efficient electron injection layers (EILs) between aluminum cathode and tris (8-hydroxyquinoline) aluminum organic light emitting diodes (OLED). The performances of devices with different thicknesses of DpDvB and DpDvBp were investigated. Experimental results show that the turn-on voltage of the devices was decreased and the luminance of the devices was enhanced with increasing thickness of the EILs. Power efficiencies of 1.07 lm/W and 0.97 lm/W were obtained by inserting a 3-nm-thick EIL of DpDvB and a 5 nm thick EIL of DpDvBp, respectively. These efficiencies are comparable to that of the device using LiF as an EIL. The results prove that DpDvB and DpDvBp layers are also suitable for efficient EILs in OLEDs.