Optical properties of multilayered Alq ₃ /α‐NPD structures investigated with spectroscopic ellipsometry

Abstract

PACS 78.20. Ci, 78.67.Pt Alternating layers consisting of tris(8-quinolinolato) aluminium (Alq 3 ) and N,N-Di(naphthalene-1-yl)-N,N`-diphenyl-benzidine (α-NPD) were prepared by organic molecular beam deposition (OMBD) in high vacuum (HV) on hydrogen passivated (111) oriented silicon. The Si(111) substrates were kept at room temperature and the deposition rate was monitored by a quartz microbalance. The typical thickness of the individual layers is in the range of 1-10 nm. The samples were studied by spectroscopic ellipsometry in the range from 0.73 to 5 eV. The evaluation of the ellipsometry measurements shows good agreement between the experimental and simulated data, assuming sharp interfaces and using the optical constants of the single layers. However, small deviations exist in the range where Alq 3 and α-NPD have absorption peaks indicating an electronic interaction at the interfaces.

A Molybdenum Dithiolene Complex asp-Dopant for Hole-Transport Materials: A Multitechnique Experimental and Theoretical Investigation

“…40 The reduced experimental data, plotted in Figure 4 as log(J) versus F 0.5 for F > 5 Â 10 4 V/cm, follow a linear relationship over 6 orders of magnitude, in good agreement with expectations from eq 1. The injection barrier φ B = 1.00 eV, derived from the Y-axis intercept of the linear fit in Figure 4, is in accord with the UPS-determined injection barrier (E F -E HOMO ) = 0.86 eV measured on the first 50 Å of the R-NPD film evaporated on a bottom Au contact (data not shown here).…”

Simulations of emission from microcavity tandem organic light-emitting diodes

“…Experimental values of the frequency-dependent dielectric functions were utilized for individual layers. Spectroscopic ellipsometry measurements 7 provided the wavelength-dependent dielectric functions of Alq 3 and α-NPB throughout the relevant wavelength range (400 to 800 nm).…”

“…In each layer of the OLED stack, the materials are represented by realistic frequencydependent absorptive dielectric functions obtained from experimental measurements for Alq 3 and NPD, 7 by measurements for Ag, 13 with measurements for ITO 14 and MoO 3 . 15 In the scattering matrix formalism the OLED is composed of layers stacked in the z direction.…”

Deep blue/ultraviolet microcavity OLEDs based on solution-processed PVK:CBP blends

“…In each layer of the OLED stack, the materials are represented by realistic frequency dependent absorptive dielectric functions obtained from experimental measurements of N, [32], Ag [33], MoO x [34] and ITO [33]. Rather than assuming that all layers are planar in the (x,y) plane we have adopted a more general formalism where the layers can have a periodic structure in the planar (x,y) directions with a repeat vector R = n 1 a 1 + n 2 a 2 , where the primitive lattice vectors are a 1 and a 2 .…”