Dependence of the emission from tris (8-hydroxyquinoline) aluminum based microcavity on device thickness and the emission layer position

Abstract

In this work, we present a systematic study of the emission from bilayer organic microcavity light emitting diodes with two metal mirrors. The devices consisting of two organic layers, N,N′-di(naphthalene-1-yl)-N,N′-diphenylbenzidine (NPB) as a hole transport layer and tris (8-hydroxyquinoline) (Alq) as emitting layer, and two metal mirrors were fabricated and characterized by transmission, reflectance, photoluminescence, and electroluminescence measurements. The effects of layer thickness, interface position, and the choice of anode (bottom mirror) were investigated.The transmission and reflectance spectra were modeled using a transfer matrix model, and the optical functions for all the materials used were determined by spectroscopic ellipsometry. The calculated and experimental data are in good agreement. The 2 dependence of the photoluminescence and electroluminescence spectra on the device thickness and interface position is discussed.

Vibrational mode contribution to the dielectric permittivity of disordered small-molecule organic semiconductors

“…We note that for Alq 3 , the isomer or the isomer ratio in the thin films studied is not specified in the references to the experimental work given. [17,18,20,22], at wavelengths λ = 1000-1500 nm. i Ref.…”

“…For many small-molecule organic semiconductor materials, the dielectric permittivity at optical frequencies is known from thin-film ellipsometry measurements [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], electron energy loss spectroscopy [27], and from theory using quantum-chemically calculated molecular polarizabilities and the Clausius-Mossotti relationship [28,29]. The relative dielectric constant at quasistatic conditions may be obtained from low-frequency capacitance-voltage (C-V) studies of sandwich-type devices [30][31][32][33][34][35][36][37][38][39].…”

Downscaling the Sample Thickness to Sub-Micrometers by Employing Organic Photovoltaic Materials as a Charge-Generation Layer in the Time-of-Flight Measurement

“…As a matter of fact, most of organic semiconductors absorb the ultraviolet (UV) light range because of their molecular nature, and therefore previous studies measured the carrier mobility by using 337 or 355 nm to be the excitation wavelength. 60 73 74 75 76 77 78 79 80 Some of organic materials, however, especially materials with a wide band gap that having either a low absorption coefficient or an absorption wavelength shorter than the deep UV light, face difficulties in selecting the excitation source and render the inaccuracy in determining the carrier mobility. 60 73 75 76 77 Therefore, a wavelength that is transparent to the wide-bandgap materials while having a high photo-response to the CGL should be a more suitable excitation source.…”

Optical properties of organic thin films deposited via organic vapour phase deposition

“…Organic semiconductors and their heterostructures have attracted considerable attention due to their application in organic light emitting devices (OLEDs) which are expected to play a significant role in various lighting and flat‐panel displays applications 1–4. These materials combine high brightness with low cost and allow large‐area fabrication onto flexible and rigid substrates 5.…”