Development and characterization of adjustable refractive index scattering epoxy acrylate polymer layers

Abstract

Abstract. Several polymer films for improved optical properties in optoelectronic devices are presented. In such optical applications, it is sometimes important to have a film with an adjusted refractive index, scattering properties, and a low surface roughness. These diffusing films can be used to increase the efficiency of optoelectronic components, such as organic light-emitting diodes. Three different epoxy acrylate mixtures containing Syntholux 291 EA, bisphenol A glycerolate dimethacrylate, and Sartomer SR 348 L are characterized and optimized with different additives. The adjustable refractive index of the material is achieved by chemical doping using 9-vinylcarbazole. Titanium nanoparticles in the mixtures generate light scattering and increase the refractive index additionally. A high-power stirrer is used to mix and disperse all chemical substances together to a homogenous mixture. The viscosity behavior of the mixtures is an important property for the selection of the production method and, therefore, the viscosity measurement results are presented. After the mixing, the monomer mixture is applied on glass substrates by screen printing. To initiate polymerization, the produced films are irradiated for 10 min with ultraviolet radiation and heat. Transmission measurements of the polymer matrix and roughness measurements complement the characterization.

Tunable High Refractive Index Polymer Hybrid and Polymer–Inorganic Nanocomposite Coatings

“…An increase in refractive index is measured across the entire wavelength range due to the incorporation of additional aromatic groups ( n poly(vinylcarbazole) = 1.683 41 ). The observed enhancement in refractive index (Δ n = +0.079) at maximum 9-vinylcarbazole loading (50% w/v) is in line with previous reports that utilize 9-vinylcarbazole to increase refractive index ( n ) using a blade coating 63 or moulding process 64 followed by UV polymerization. Overall, greater refractive indices are achieved in the present study by utilizing a higher refractive index host polymer.…”

Large-Area Screen-Printed Internal Extraction Layers for Organic Light-Emitting Diodes

“…The BMA was added in order to lower the viscosity for better nanoparticle dispersion, whereas the BDDMA was used to improve the hardness of the final layers. To increase the refractive index of the matrix material, 35.27 wt % of the total mixture contained 9-vinylcarbazole (Sigma-Aldrich). , Furthermore, 8.82 wt % titanium oxide (TiO 2 ) nanoparticles (P25, Evonik, mean primary particle diameter 21 nm) was added to further increase the mean refractive index of the extraction layer, as well as to introduce volume scattering by agglomerated nanoparticles. Further additives were 0.88 wt % 2-(2-methoxyethoxy)­ethoxy]­acetic acid (Clariant) for particle stabilization, 1.59 wt % benzophenone (Sigma-Aldrich) for UV polymerization, and 0.54 wt % lauroyl peroxide (Sigma-Aldrich) for further thermal hardening.…”