The Effect of Annealing of Organic Thin Films on Charge Injection in Organic Electroluminescent Devices

The effect of annealing of organic thin films on charge injection in the tris(8-quinolinolato)aluminium (Alq3)-based organic electroluminescent (EL) devices was investigated. The external quantum and luminous efficiencies were found to improve by annealing. The investigation of the effect of annealing on charge injection in hole-only and electron-only devices has revealed that while hole injection from the ITO electrode into the hole-transport layer is not affected by the annealing, electron injection from the MgAg electrode into the Alq3 layer is enhanced by the annealing. It is concluded that improved charge balance due to the enhanced electron injection by the annealing is responsible for the improvement of the performance of the organic EL device.