Effect of Reactive Self-Assembled Monolayer at the Anode Interface of Organic Light-Emitting Diode

Organic light-emitting diodes (OLEDs) were prepared on indium-tin oxide (ITO) substrates that were modified with various self-assembled monolayers (SAMs) including those which have reactive terminal units. The OLED performance was analyzed in terms of molecular length, dipole moment and HOMO level of SAM molecules estimated by the density functional theory calculation. It was suggested that the current efficiency of OLED is partly improved by controlling the carrier balance, interfacial dipole moment, and electron energy level by SAM modification. More importantly, remarkable improvement in OLED efficiency was achieved by chemically tethering the inorganic/organic interface via benzophenone-terminated SAM. The reactive SAM having benzophenone terminal group can be a promising tool to control the inorganic/organic interface for organic devices.