In this talk the current knowledge of the electrical degradation during fatigue of polymer-based light-emitting diodes is reviewed focusing especially on derivatives of poly(p-phenylenevinylene) (PPV). Studied are observed phenomena, mechanisms and material properties changing during continuous device operation at constant current. This talk focuses on the effect of chemically induced defects introduced during synthesis and elaborates their influence on transport properties such as charge carrier mobility and device lifetime. Highlighted will be the influence of a halogen defect that leads to a degradation of the electrodes and therewith is mainly responsible for device degradation. In addition, an optical effect will be described in which the absorption of the emitted electroluminescence by the semiconductor itself is one of the reasons for device degradation. Finally, the influence of the triplet density is investigated indicating that local deposition of energy is also an important factor to contribute to degradation. All experiments were accompanied by theoretical modeling shining light on how the change of injection barriers, charge carrier mobility or trap density influence the current-voltage characteristics of the diodes. Especially interesting is thereby the consideration of image charges for low carrier densities through the Schottky effect, which allows for an enhanced barrier lowering, and a more realistic description of the device performance.
