Degradation of Ru$\left( {{\text{bpy}}} \right)_3^{2 + }$-based OLEDs

Abstract

Analysis of the possible mechanisms of degradation of Ru$\left( {{\text{bpy}}} \right)_3^{2 + }$-based OLEDs has led to the idea of quencher formation in the metalloorganic area close to the cathode. It has been suggested that the quencher results from an electrochemical process where one of the bipyridine (bpy) groups is replaced with two water molecules [1] or from reduction of Ru$\left( {{\text{bpy}}} \right)_3^{2 + }$ to Ru$\left( {{\text{bpy}}} \right)_3^0$ [2]. We have tested these and other degradation ideas for Ru$\left( {{\text{bpy}}} \right)_3^{2 + }$-based OLEDs, both prepared and tested with considerable exposure to the ambient environment and using materials and procedures that emphasize cost of preparation rather than overall efficiency. In order to understand the mechanisms involved in these particular devices, we have correlated changes in the devices' electrical and optical properties with MALDI-TOF mass spectra and UV-vis absorption and fluorescence spectra.