Abstract: The invention relates to a polymer optoelectronic device comprising at least a transparent conductive oxide layer, an active polymer layer, a back electrode layer and a substrate layer, wherein the transparent conductive oxide (TCO) layer has a controlled surface structure which is characterised by having an X-value in the range of from 10 nm to 500 nm, and a Y-value in the range of from 15 nm to 1000 nm, wherein the ratio between the X-value and the Y-value (X/Y) is at most 1, whereby the X-value is defined as the average value of the height of the peaks on the surface, the Y-value is defined as the average peak to peak distance on the surface, and both the X and Y values are measured by means of SEM (Scanning Electron Microscopy) or Atomic Force Microscopy (AFM).