Planarized and Compact Light Scattering Layers Based on Disordered Titania Nanopillars for Light Extraction in Organic Light Emitting Diodes

• Published in: Advanced optical materials Vol. 9; no. 14
• Main Authors: Donie, Yidenekachew J., Theobald, Dominik, Moghadamzadeh, Somayeh, Mertens, Adrian, Hossain, Ihteaz M., Paetzold, Ulrich W., Lemmer, Uli, Gomard, Guillaume
• Format: Journal Article
• Language: English
• Published: 01.07.2021
• Subjects: light outcoupling; light scattering; organic light emitting diodes; phase‐separated nanostructures; TiO 2 nanopillars
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202001610

In this work, the extraction of waveguided and substrate modes in organic light emitting diodes (OLEDs) is improved by using compact light scattering layers composed of a disordered 2D array of TiO2 nanopillars. The TiO2 nanopillars are fabricated by combining a self‐assembly and a solvent‐assisted lift‐off process, and are further planarized by a 250 nm thin epoxy‐based photoresist layer to facilitate their anode deposition and integration within the OLED stack. This fabrication route allows engineering internal light outcoupling elements with a limited amount of parasitic absorption and with easily tunable light scattering properties that are effective over a broad spectral and angular range. Taking the example of a monochromatic bottom emitting OLED (λpeak = 520 nm), the authors demonstrate an efficiency enhancement of +22%rel upon the incorporation of the planarized light extraction layer as well as ameliorated angular emission characteristics. This approach can be integrated in a high‐throughput fabrication routine and straightforwardly extended to other OLED layouts. A versatile method for the fabrication of light scattering layer composed of a disordered 2D array of titania nanopillars is proposed. The authors demonstrate the benefits of the nanopillars by incorporating them in organic light emitting diode (OLED). Prior to the OLED deposition, the nanopillars are planarized by a photoresist layer to facilitate their integration within the OLED stack.