The fabrication of organic photodiodes on solution cast indium tin oxide (ITO) bottom electrodes on flexible substrates is described. ITO coatings with a sheet resistance of 2 to 3 k Omega/sq are produced by gravure printing process on PEN (polyethylene 2,6-naphthalate) films. The ITO films are directly used as transparent bottom electrodes for organic photodiodes (OPD). Furthermore, first experiments to integrate one of these OPDs in an all-organic opto-chemical sensor are successfully demonstrated. The implementation of OPDs as detectors in applications such as integrated sensors demands a fabrication of these devices on flexible substrates. For these applications the OPDs on printed ITO on PEN are especially suitable. (C) 2009 Elsevier B.V. All rights reserved.