The Hole Injection Layer (HIL) is one of several layers of self-luminous Organic Light Emitting Diodes(OLED). The HIL layer is directly deposited on the anode, and charge transport occurs through hole electrodes (holes).
Due to the voltage difference between the anode and cathode, the HIL layer supports hole injection from the anode to the organic layers. Hole transport to the emission layer( EML) is performed by the hole transport layer( HTL). The recombination of electrons from the Electron Transport Layer( ETL) with the holes coming from the HTL layer produces photons as visible light.