Effect of UV treatment on anode surface in organic EL displays

Abstract We investigated the effect of UV treatment on the anode surface in three-organic-layer-structure devices. UV treatment in an O 2 –N 2 ambient environment improved device characteristics as follows: (i) the drive voltage was shifted lower, (ii) the number of dark spots was decreased, and (iii) the storage stability was increased. To understand the mechanism of these phenomena, thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) were used for surface analysis of the anode. In addition, XRD was used for structural analysis of CuPc. Photoresist residue after the anode patterning process was completely removed by UV treatment. Furthermore, we have observed that nitrogen oxide (NO x ) adhered to the anode surface. This may result in improvement of current injection from anode surface to CuPc layer.