Effect of UV treatment on anode surface in organic EL displays

We investigated the effect of UV treatment on the anode surface in three -o rganic -layer-structure devices. UV treatment in an O-2-N-2 ambient environ ment improved device characteristics as follows: (i) the drive voltage was shifted lower, (ii) the number of dark spots was decreased, and (iii) the s torage stability was increased. To understand the mechanism of these phenom ena, thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscop y (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 struc tural analysis of CuPc. Photoresist residue after the anode patterning proc ess was completely removed by UV treatment. Furthermore, we have observed t hat nitrogen oxide (NOx) adhered to the anode surface. This may result in i mprovement of current injection fi om anode surface to CuPc layer. (C) 2000 Elsevier Science S.A. All rights reserved.