Electron injection and transport mechanisms of an electron transport layer in OLEDs

Electron injection and transport are key issues in the performance of organic light-emitting diodes (OLEDs). In this paper, an efficient n-doped electron transport layer (ETL) composed of 4,7-diphenyl-1,10-phenanthroline (Bphen) and lithium acetate (CH₃COOLi) is demonstrated. The results reveal that the Fermi level moves toward the lowest unoccupied molecular orbital (LUMO), which consequently reduces the electron injection barrier and further enhances the efficiency of electron injection from the aluminum cathode. The mobility of electrons in the Bphen layer increased with CH₃COOLi doping. In addition, a sky-blue fluorescent OLED was fabricated using the CH₃COOLi-doped Bphen ETL, exhibiting a high luminance and efficiency. We also proved that as an n-type dopant, LiAC is more capable than LiF.