Flexible organic light-emitting diodes with ZnS/Ag/ZnO/Ag/WO3 multilayer electrode as a transparent anode

• Published in: Organic electronics Vol. 15; no. 10; pp. 2468 - 2475
• Main Authors: Yang, Dae Young, Lee, Sung-Min, Jang, Woo Jae, Choi, Kyung Cheol
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2014; Elsevier
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electroluminescence; Electronics; Exact sciences and technology; Flexible electronics; Flexible organic light-emitting diodes; Fullerenes and related materials; Multilayer electrodes; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Optoelectronic devices; Other luminescence and radiative recombination; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transparent electrodes; Visible and ultraviolet spectra; Flexible electronics; Transparent electrodes; Multilayer electrodes; Flexible organic light-emitting diodes; Performance evaluation; Transparency; Hole; Anode; Ductility; Electroluminescence; Flexibility; Microcavity; Zinc sulfide; Tungsten oxide; Tin addition; Sheet resistivity; Optical properties; Optoelectronic device; Optical characteristic; Zinc oxide; Visible spectrum; Electrical characteristic; Organic electronics; II-VI compound; Electrical properties; Doped materials; Multiple layer; Absorption coefficient; Transmittance; Indium oxide; Hole injection layer; Thickness; Flexible structure; Organic light emitting diodes; Transparent material; Charge carrier injection
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2014.06.021

•We propose a low resistive (2.17Ω/sq.) transparent and flexible multilayer electrode for OLEDs.•The high luminous transmittance (82%) is a result of the asymmetric design of Ag layers.•The ZnS/Ag/ZnO/Ag/WO3 based OLED performance is comparable to or even better than of ITO based OLED.•The ZnS/Ag/ZnO/Ag/WO3 based OLED performance is strongly affected by microcavity effect. We investigated the highly flexible, transparent and very low resistance ZnS/1st Ag/ZnO/2nd Ag/WO3 (ZAZAW) multilayer electrodes on PET substrate as an anode in flexible organic light-emitting diodes (OLEDs). A theoretical calculation was first conducted to obtain the optimal thickness of the ZAZAW multilayer for high transparency. Its measured luminous transmittance was over 80% in the visible range with a very low sheet resistance of 2.17Ω/sq., and it had good mechanical flexibility due to the ductility of Ag. Ag’s effect on optical and electrical properties was also studied. Flexible OLEDs devices that were fabricated on ZAZAW multilayer anode showed good hole injection properties comparable to those of ITO-based OLEDs due to the use of WO3 as a hole injection layer. However, the electroluminescent properties of the ZAZAW-based OLEDs varied depending on WO3 thickness. Although the transmittance of the ZAZAW electrode was reduced by tuning the WO3 thickness to adjust the microcavity effect, the device efficiency could be enhanced above that of ITO-based OLEDs.