Preparation of Parylene-N ultrathin films and their applications in organic light emitting diodes

Ultrathin poly-p-xylylene (PPXN) films were prepared by using a home-made Knudsen cell (KC). By special design and optimization of the KC, the growth rate was well controlled in the range of 0.01nm/s -0.02 nm/s at room temperature in a relatively lower reaction pressure of 10-3 Pa. The PPXN films were identified by infrared (IR) spectra. The morphology of PPXN films were measured by atomic force microscope (AFM). It was resulted that the PPXN surface showed a spike-free undulated morphology. The well controlled PPXN thin films were used as buffers in organic light emitting diodes to control carrier injection and transport, and improvements of more than 80% in device current efficiency were achieved.