Abstract
In flexible OLEDs (FOLEDs), the traditional ITO anode has disadvantages such as refractive-index mismatches among substrate and other functional layers, leads to light loss of nearly 80%, meanwhile, its brittle nature and lack in raw materials hinder its further applications. We investigated an efficient FOLED using a semi-transparent silver (Ag) anode, whereas the device was built on a nano-corrugated flexible polycarbonate (PC) substrate prepared by thermal nanoimprint lithography. The corrugations were well preserved on each layer of the device, both the micro-cavity effect and surface plasmon polariton (SPP) modes of light loss were effectively suppressed. As a result, the current efficiency of the FOLED using a conformal corrugated Ag anode enhanced by 100% compared with a planar Ag anode device, and enhanced by 13% with conventional ITO device. In addition, owing to the quasi-periodical arrangements of the corrugations, the device achieved broad spectra and Lambertian angular emission. The Ag anode significantly improved the bending properties of the OLED as compared to the conventional ITO device, leading to a longer lifetime in practical use. The proposed manufacturing strategy will be useful for fabricating nano corrugations on plastic substrate of FOLED in a cost-effective and convenient manner.
Highlights
In recent years, display technologies are grasping researchers’ best interest in aspects of transparent and flexible applications.[1]
Significant research efforts have recently focused on replacing Indium tin oxide (ITO) transparent electrodes in flexible Organic light emitting diode (OLED) (FOLEDs)
The current efficiency of the corrugated flexible OLED (FOLED) device increased by 100% compared with the planar Ag anode device
Summary
The spectrum of the OLED narrowed as a result of the micro cavity effect, this potentially leading to unexpected performance in practical applications such as lighting. TYu-Hsuan Ho used a mask of polystyrene (PS) spheres to fabricate a Ag film with mesh structures.[16] This silver film, used in replacement of the ITO anode, showed improved transmittance versus the planar metal film, and a micro lens array was fabricated on the substrate to further improve the light efficiency. The quasi-periodically distributed corrugations allowed us to effectively solve issues such as the spectra narrowing and viewing angle dependency, which are the intrinsic effects in traditional planar metallic micro-cavity OLEDs. the bending property greatly improved compared with that of the ITO device, leading to longer practical lifetimes
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