Organic light-emitting devices with triphenylphosphine oxide layer

We have developed organic light-emitting devices using triphenylphosphine oxide (Ph₃PO) layers. The operating voltage of device is substantially reduced by using a Ph₃PO layer. For example, the required voltages for a current density of 20 mA/cm² are 3.5 and 9.7 V for the devices with Ph₃PO and Alq₃ layers, respectively. Good electron transporting property of Ph₃PO results in a high luminance of 1000 cd/m² at a low driving voltage of 4.1 V in a device with a structure of ITO/2-TNATA (15 nm)/α-NPD:rubrene (1%, 10 nm)/α-NPD (30 nm)/Ph₃PO (60 nm)/LiF (0.5 nm)/Al.