Hybrid organic–inorganic materials for integrated optoelectronic devices

Abstract

A device containing a microcavity organic light‐emitting diode (OLED) and a magnetooptically active bismuth iron garnet (BIG) Bi3Fe5O12 waveguide combines a planar source for polarized light generation with the material exhibiting the highest known Faraday rotation at room temperature. To build such a device an optimization of garnets and OLEDs has to be done. For a good functionality of the device it is essential to maximize the light coupled from the OLED into the waveguide and to seperate s‐ and p‐polarized emitted light. To optimize the OLED emisson numerical simulations have been performed where material and thickness of the metal anode, as well as the thickness of the hole and the electron conducting layers were varied. The stacks with the best separation of s‐ and p‐polarized light and the highest coupling into the waveguide were determined, fabricated, and characterized regarding their electrical and optical properties. OLEDs have to be deposited on plane surfaces for exhibiting low leakage currents and thus being functional. In order to get plane and crack free BIG surfaces the garnet growth and surface formation were examined on various gadolinium gallium garnet (GGG) Gd3 Ga5 O12 and buffered non‐garnet substrates. GGG substrates with different cuts and lattice constants were characterized as well as yttrium iron garnet (YIG) Y3Fe5O12 and GGG buffered sapphire, silicon, and fused silica substrates. The garnet had to be structured to fabricate a planar waveguide. Therefore laser structuring and plasma etching techniques were utilized. The structured garnets were characterized regarding the wall roughness. The optical constants of YIG and BIG were determined from films deposited on silicon using ellipsometric measurements. The combination of microcavity OLED and garnet waveguide resulted in an integrated magnetooptical modulator whose functionality has been proven by applying an external magnetic field and measuring the rotation of the polarized light.

Simulations of emission from microcavity tandem organic light-emitting diodes

“…8(b)]. The p-polarized emission is weaker than the s-polarized emission, similar to the results of Wehlus et al 22 and Reinke et al 20 The tandem microcavity device has superior angular emissivity compared to the single microcavity OLED. In both s-and p-polarizations the tandem microcavity OLED displays a peak emission in the normal direction at the wavelength of 520 nm, which remains the peak emission intensity upto viewing angles of ∼30 deg (Figs.…”

“…In all cases there is negligible intensity at a large viewing angle. As found in earlier studies [20][21][22] the strong polarization and angular dependence of the emission is a marked signature of microcavity effects in the OLED, and places constraints on the application of microcavity OLEDs for lighting applications. The emission spectra are also very dependent on the thickness of the emitting layers in the OLED, which needs to be optimized accurately to achieve the brightest OLEDs.…”

“…[20][21][22] Hence we simulated the angular emissivity of our microcavity OLEDs. For the single microcavity device we find [ Fig.…”

Transition Metal Oxides for Organic Electronics: Energetics, Device Physics and Applications

“…The effective protection that WO 3 provides against ITO sputtering has been attributed to the nano‐crystalline packing of WO 3 clusters that form a dense layer. TMOs show also high scattering and absorption cross‐section for ions and X‐rays,156, 157 which additionally hinder particles such as Ar + , Ar, O − and O 2 − present during the sputtering process from penetrating deep into the organic layer. It is important to note that for each reported sputtering buffer layer, an optimized sputtering process is essential with low power levels for the deposition of the first few nanometers to minimize the impact of energetic particles.…”

Dynamical X‐ray diffraction theory: Characterization of defects and strains in as‐grown and ion‐implanted garnet structures

“…The choice of the as-grown and ion-implanted synthetic garnet crystals and films as our investigation objects was caused by the circumstance that many functional materials used in modern devices have a complicated multicomponent structure including also the structural imperfections and inhomogeneous strain distributions, which can substantially influence their physical properties (see, e.g., Refs. [13][14][15][16]). On the other hand, the synthetic garnet systems themselves are of great interest for both basic scientific research [17][18][19][20][21][22][23] as well as various practical applications in magnetic, optical, and magneto-optical devices, etc.…”