Effect of Alkyl Chain Length of Fluorinated Self-Assemble Monolayer to Organic Light-Emitting Diodes as a Hole Injection Layer

The introduction of fluorinated self-assembled monolayer (FSAM) enhanced hole injection from indium tin-oxide (ITO) and improved device lifetime for organic light-emitting diodes. These effects were caused by the large dipole moment of FSAM molecule. We studied the effect of fluorinated alkyl chain length. Although the increase in alkyl chain let to the increase in dipole moment, it also meant the increase in insulating part. However, a small increase in alkyl chain did not influence the enhancement of hole injection from ITO. A short alkyl chain disturbed the regular formation of SAM by lowering an intermolecular interaction.