Analysis of the injection layer of PTCDA in OLEDs using x-ray photoemission spectroscopy and atomic force microscopy

Through the investigation of the sample surface and interface of 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA)/indium-tin-oxide (ITO) thin films using atomic force microscopy, it has been found that the surface is complanate, the growth is uniform and the defects cover basically the surface of ITO. Furthermore, the number of pinholes is small. The analysis of the sample surface and interface further verifies this result by using x-ray photoemission spectroscopy . At the same time, PTCDA is found to have the ability of restraining the diffusion of chemical constituents from ITO to the hole transport layer, which is beneficial to the improvement of the performance and the useful lifetime of the organic light emitting diodes (OLEDs).