Enhanced Light Extraction from Mechanically Flexible, Nanostructured Organic Light‐Emitting Diodes with Plasmonic Nanomesh Electrodes

Abstract

cost-effectiveness, reliable fl exibility, high transmittance, low resistance, in conjugation with stable device operation. Especially, high transmittance and low sheet resistance have been regarded as vital factors evaluating the electrode performance since they are directly associated with the device effi ciency.A nanomesh-type metal fi lm is one of the most attractive alternatives for transparent and fl exible electrodes, because it is comparatively free of the typical tradeoff relation between high transmittance and low sheet resistance due to assistance of surface plasmon polariton (SPP) for enhancing the transmittance. [ 16,[18][19][20] Metal nanomesh electrodes with transmittance levels over 80% in the entire visible range without compromising degradation of sheet resistance (<1 Ω sq −1 ) were reported theoretically, [ 21 ] and also such high-performance metal nanomesh electrodes were demonstrated experimentally. [ 22 ] Moreover, the feasibility of their application to OLED devices has been sequentially studied, in which another positive effect of experimental improvement of the device effi ciency was found. [ 14,16 ] Possible reasons for this effi ciency improvement are high transmittance of the metal nanomesh electrode or reduction of waveguide loss in OLED layers, but to the best of our knowledge, explicit reasons have not been unveiled so far. In particular, high transmittance of metal nanomeshes has been generally considered as a fundamental requirement for highly effi cient OLEDs due to the expectation that an increase in the electrode transmittance is the straightforward way to extract the light emitted from the device. However, contrary to this expectation, here we report that high transmittance of periodic metal nanomesh electrodes does not always facilitate attaining the high effi ciency of OLEDs incorporating such nanomesh electrodes. Systematic investigation on metal nanomesh anodes with various periods at fi xed thicknesses of comprising layers in green OLEDs explains that great improvement of the light extraction effi ciency is caused by signifi cantly suppressed SP loss that is available due to inherent nanostructures of organic and cathode layers, not by the microcavity effect. The optimal nanomesh period for high extraction effi ciency of the device does not correspond to that for high transmittance of the electrode, indicating that high-performance OLEDs can be achieved without a highly transparent electrode.Characteristics of light extraction from nanostructured organic light-emitting diodes (OLEDs) incorporating plasmonic metal nanomesh anodes are investigated for achieving high-performance, fl exible OLEDs. Given that fl exibility of devices is limited by rigid and fragile constituents such as indium tin oxide electrodes, alternative transparent, and fl exible electrodes including nanomesh-type metal fi lms have been widely studied, where high transparency, low resistance, and good fl exiblity were regarded as essential requirements of high-performance fl exible applications due to the...

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DNA as Functional Material in Organic-Based Electronics

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Thin-film organic semiconductor devices: from flexibility to ultraflexibility

“…To further enhance the light extraction or light trapping in the devices, nanostructures or nanoparticles are introduced into these TFC electrodes for improving the device performances [47,[130][131][132][133][134][135][136][137][138][139][140]. Besides these thin-film electrodes, fiber-/mesh-shaped electrodes also demonstrated good flexibility [17,51,64,67,68].…”

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