Effect of conductivity of hole injection layer on the performance of a blue light emitting solution processable OLED

The performance of blue emitting OLED devices, using a polyspiro as blue light emitting polymer, were studied as a function of the conductivity of a novel hybrid hole injection material. The hole injection material is based on a polyarylamine using a molecular magnet as oxidant. The charge density and the luminance of the devices changed considerably with increasing conductivity of the hole injection layer. The change in device performance can be attributed to a change from a hole limited device to a balanced charge carrier device and eventually to an electron limited device. The performance of the optimized device configuration is significantly improved with respect to a device making use of PEDOT:PSS as the hole injection layer reaching efficacies of 3.5 cd/A at 5000 cd/m 2 .