Improved performance of organic light-emitting diodes with cesium chloride inside tris (8-hydroxyquinoline) aluminum

A series of small molecular organic light-emitting diodes (OLEDs) based on tris (8-hydroxyquinoline) aluminum (Alq3) was fabricated by varying thicknesses and positions of cesium chloride (CsCl) layer inside Alq3 layer. Both luminance and efficiency are enhanced due to the improvement of electron injection when a CsCl layer was deposited between Alq3 and aluminum (Al). For the insertion of the CsCl layer at the 10 nm position inside Alq3 layer away from Al cathode, the enhanced current density and luminance are attributed to the reaction between diffused Al and Cs. And the efficiency and luminance are enhanced due to the trap sites induced by the CsCl layer at the distance of 20 and 30 nm away from the Al cathode. The current density and luminance of devices, in which various thicknesses of CsCl layer was inserted at 20 nm position inside Alq3 layer away from the Al cathode, is affected by both hole trapped and insulating layer effects.