Fabrication and Characteristics of Self-Assembled Monolayer of Oligophenylene Ethylene and Its Application in OLEDs

Abstract

We have synthesized 4-[(4-nitrophenyl)ethynyl]benzoic acid (NPBA) as a hole injection material for the modification of ITO surface and fabricated OLEDs consisting of ITO/NPBA self-assembled monolayer (SAM)/TPD (600 Å)/Alq₃ (600 Å)/Al (600 Å). The effects of ITO modified with NPBA SAM exhibited lower driving voltage than the device using 4-nitrobenzoic acid (NBA). Also, we have examined the interface properties between the modified ITO and adjacent organic layer from the measurements of contact angle and atomic force microscopy (AFM).

Keywords:

• 4-[(4-nitrophenyl)ethynyl]benzoic acid (NPBA)
• interface property
• ITO, organic light emitting diode
• self-assembled monolayer

Acknowledgments

This work was supported by the Basic Research Program of the Korea Science & Engineering Foundation (R01-2006-000-10196-0).

Notes

γ _s ^p : polar component, γ: surface energy, the sum of polar and dispersive component.