Evidence for Solid State Electrochemical Degradation Within a Small Molecule OLED

Acridone derivative have been synthesised and used as OLED (Organic Light Emitting Diode) emitters which were found to be electroactive. Electrochemical investigations showed a side reaction takes place inside an active layer which diminished the overall device efficiency. By using a dopant and host active layer architecture, the formation of the by product was removed. The by-product was identified as a σ-dimer formed inside an oligomer. The active layers were investigated by electrochemical techniques (cyclic voltammetry, UV-Vis-NIR spectroelectrochemistry, Electron Paramagnetic Resonance (EPR) spectroelectrochemistry and Dynamic Electrochemical Impedance Spectroscopy (DEIS)) to characterize the layers, charge carriers, and electronic energy levels. It is clear from these observations that electrochemical reactions of emitter molecules in a working devices is a route to device degradation.