Inverted OLED Cathode Using Cesium Carbonate Dipole Layer

The patent changes the cathode material from low work function metal (magnesium) to high work function metal (aluminum), and introduces a dipole layer (cesium carbonate) to modify the electronic structure at the cathode interface. This parameter change in material composition and electronic structure achieves both good electron injection and oxidation resistance

The patent creates a composite cathode structure consisting of aluminum metal layer combined with a dipole layer of cesium carbonate. This composite structure combines the oxidation resistance of aluminum with the electron injection enhancement from the dipole layer, resolving the contradiction between these two properties

The patent uses aluminum as the cathode material, which inherently provides an inert, oxidation-resistant environment that protects against water and oxygen. The aluminum surface forms a stable oxide layer that prevents further degradation, creating a protective inert environment for the device

The dipole layer of cesium carbonate acts as an intermediary between the aluminum cathode and the organic electron transport layer. It modifies the electronic structure to enhance electron injection while the aluminum underlying structure provides oxidation resistance, mediating between these two requirements