Effects of CsF/Metal Interface on Electron Injection in Polymer Light-Emitting Diodes

Abstract

The effect of electron injection in polymer light-emitting diodes has been investigated at the interface between the CsF layer and metals of the cathode. Efficient electron injection was achieved when the thickness of the CsF layer deposited on the organic layer was 1.5 nm. When the thickness of the MgAg layer deposited on the CsF layer was more than 1 nm, efficient electron injection was achieved. For the device with a 1.5-nm-thick CsF and a 1-nm-thick MgAg cathode, the deposition orders of CsF and MgAg were independent of efficient electron injection. That is, the coexistence of CsF and MgAg near the organic layer resulted in efficient electron injection. To achieve efficient electron injection, we found that was sufficient device performance was obtained when the surface of the organic layer with CsF was covered with approximately 25% MgAg.