Enhanced light extraction efficiency and viewing angle characteristics of microcavity OLEDs by using a diffusion layer

• Published in: Scientific reports 2021-02, Vol.11 (1), p.3430-10, Article 3430
• Main Authors: Park, Cheol Hwee, Kang, Shin Woo, Jung, Sun-Gyu, Lee, Dong Jun, Park, Young Wook, Ju, Byeong-Kwon
• Format: Article
• Language: English
• Subjects: 639/166/987; 639/624/1020/1091; 639/624/399/1098; 639/766/1130/2799; Diffusion; Efficiency; Etching; Humanities and Social Sciences; multidisciplinary; Polymers; Polymethylmethacrylate; Science; Science (multidisciplinary); Zinc oxide; Zinc oxides
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-82753-9

The viewing angle characteristics and light extraction efficiency of organic light-emitting diodes (OLEDs) with a micro-cavity structure were enhanced. This was accomplished by inserting a diffusion layer composed of nano-sized structures of a transparent polymer poly(methyl methacrylate) (PMMA) combined with a zinc oxide (ZnO) semi-planarization layer with a high refractive index (n = 2.1) into the devices. The PMMA nanostructures were fabricated by employing a reactive ion etching (RIE) process. The height and density of the PMMA nanostructures were controlled by varying the speed at which the PMMA was spin-coated onto the substrate. The insertion of the diffusion layer into the micro-cavity OLEDs (MC-OLEDs) improved the external quantum efficiency (EQE) by as much as 17% when compared to that of a MC-OLED without a diffusion layer. Furthermore, adjustment of the viewing angle from 0° to 60° halved the peak shift distance of the electroluminescence (EL) spectra from 42 to 20 nm. Additionally, changing the viewing angle from 0° to 60° changed the color coordinate movement distance of the MC-OLED with the diffusion layer to 0.078, less than half of the distance of the MC-OLED without the diffusion layer (0.165).