Interface Phenomena of Self-Assembled Monolayer with Various Alkyl Chain as a Hole-Injection Layer for Organic Light-Emitting Diodes

Abstract

We investigate the effect of the interface phenomena of a self-assembled monolayer (SAM) molecules on hole injection. A SAM represents an easy and accurate approach to the modification of surface properties. The dipole moment of a fluorinated SAM (FSAM) improves hole injection from Indium Tin Oxide (ITO). We prepare several kinds of FSAM with different number of fluorine atoms FnSAM. As the number of fluorine atom increases, the dipole moment also increases. Increasing the chain length increases the van der Waals interaction between alkyl chains. We examine the interface characteristics of SAM molecules on the hole injection.

Effects of Self-Assembled Monolayers with Fluorinated Alkyl Chain

“…The effect of a work function is related to the N mcosu/ee 0 from the Helmholtz equation. N is the density of dipoles (cm ¡2 ), m is the dipole moment (debyes), u is the average angle that the dipole makes with the surface normal, e is the permittivity of free space and e r is the dielectric constant of the FSAM [10,11]. The work functions of F3SAM, F8SAM, F10SAM, F12SAM and a-NPD were estimated to be 5.40, 5.43, 5.45, 5.46 and 5.48 [eV], respectively.…”

Enhancement of the Luminance Efficiency due to an Embedded Self-Assembled Monolayer in Organic Light-Emitting Devices

“…Some studies on the utilization of a self-assembled monolayer (SAM) as a surface dipolar layer have been conducted to modify the work functions of the transition metal, metal oxide, and inorganic electrodes. [20][21][22][23] The SAM adsorbed on the indium-tin oxide (ITO) layer significantly affects the work function of the ITO layer owing to the variation of the molecular dipole. [20][21][22][23][24][25][26] Even though some investigations concerning the electrical and optical properties of the OLEDs with an SAM have been performed, studies on the enhancement of the electrical and optical properties as well as the luminance efficiency due to an embedded SAM in OLEDs have not been conducted yet.…”

“…[20][21][22][23] The SAM adsorbed on the indium-tin oxide (ITO) layer significantly affects the work function of the ITO layer owing to the variation of the molecular dipole. [20][21][22][23][24][25][26] Even though some investigations concerning the electrical and optical properties of the OLEDs with an SAM have been performed, studies on the enhancement of the electrical and optical properties as well as the luminance efficiency due to an embedded SAM in OLEDs have not been conducted yet. This paper shows data for the enhancement of the luminance efficiency due to an embedded SAM in OLEDs.…”