蜂巢结构

Materials Chemistry C
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Institute of Functional Nano & So Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China. E-mail: zkwang@; lsliao@; Fax: +8665882846; Tel: +86-512-65880945 † Electronic supplementary information (ESI) available: The average performance of honeycomb structured OLED devices based on Alq3 as the emitter with the thicknesses of the MoOx layer increasing from 30 to 70 nm and the O2 plasma etching time varying from 3 to 6 min. See DOI: 10.1039/c4tc02596b
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See Zhao-Kui Wang, Liang-Sheng Liao et al., J. Mater. Chem. C, 2015, 3, 1666.
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The authors demonstrate a honeycomb structured organic light-emitting diode (OLED) with high enhancements greater than 2.0 fold and 2.3 fold in current efficiency and power efficiency, respectively. The dispersion relationships in both planar and nano-honeycomb structured OLEDs are calculated through numerical simulations utilizing the finite-difference time-domain method and measured through the electroluminescence spectra. There is good agreement between the numerically calcul decades, organic light-emitting diodes (OLEDs) have grown to be one of the most promising candidates for applications in displays and solid-state lighting, primarily owing to their high efficiency, high colour-rendering index, exibility, and so on.1–5 Despite the high internal quantum efficiency of OLEDs, their external quantum efficiency is typically less than $30% due to the poor out-coupling efficiency which is mainly restricted by the light loss mechanisms in OLEDs including the substrate mode (light trapped inside the glass substrate), ITO/organic waveguide mode (light trapped inside the ITO/organic layer), surface plasmon-polariton (SPP) mode (light transforming into the mode travelling along the interface of the organic layer and the Al cathode) and so on.6–11 Therefore, light extraction remains one of the important issues in OLEDs and micro/nano-structures are always good techniques for light extraction, such as introducing microlens arrays on the back of the substrate to extract the substrate mode12–14 and incorporating gratings into the device structure to extract the ITO/organic mode and SPP mode.15–21 Nevertheless, most reported light-extraction techniques require e-beam and/or interference lithography to fabricate periodic microstructures as templates or directly on the substrate. These are not compatible with the manufacturing of low-cost and large-area OLEDs.
Nanosphere lithography has been proven to be a exible and cost-effective technique for the patterning of nanostructured arrays with long-range periodicity in a large scale.22–24 Photonic crystal (PC) structures formed through nanosphere lithography have been widely studied in the light emitting diodes (LEDs) to greatly enhance their power efficiency.25–29 For example, Yoon et al. demonstrated three types of 2D PC arrays (nanospheres, nanoholes, and nanobowls) fabricated based on the monolayer 单层溶胶晶 聚苯乙烯微球 colloidal crystal (MCC) pattern of polystyrene spheres (PS) in 体 order to enhance the luminous efficiency of Y3Al5O12:Ce3+ yellow ceramic plate phosphor-capped high-power white LEDs.25 In GaN-based LEDs with different sizes of ITO nanobowls PC structures on a p-GaN layer have been proposed and demonstrated by Wu et al. Under an injection current of 350 mA, the improvement in light output power has reached about 63.5%, compared with the reference LED with a planar ITO layer.28 In this work, we introduced a nano-honeycomb structure into OLEDs by forming the MCC pattern of PS on ITO substrates 纳米球光刻技术 via the nanosphere lithography technique. MoOx is used as the buffer layer lled into the gaps of MCC templates owing to its good hole injection and hole transport characteristics.30,31 Particularly, the hole injection/transport capability of MoOx in OLEDs rarely changes with the thickness aer a UV-Ozone treatment.32 High enhancements greater than 2.0 fold and 2.3 fold are achieved for the current efficiency and the power efficiency, respectively, in red phosphorescent OLEDs based on the iridium(III)bis(2-methyldibenzo-[f,h]quinoxaline)(acetylacetonate) (Ir(MDQ)2(acac)) emitter. The origin of improved light outcoupling efficiency in nano-honeycomb structured OLEDs is systematically studied. From the dispersion relationships calculated by the nite-difference time-domain (FDTD) numerical simulations, the extracted energy in nano-
Showcasing research from Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University. Title: Origin of light manipulation in nano-honeycomb structured organic light-emitting diodes Nano-honeycomb structured organic light-emitting diodes were constructed. The origin of the large enhancement in device performance was systematically analyzed through experimental measurements and numerical simulations.
Received 13th November 2014 Accepted 13th January 2015 DOI: 10.1039/c4tc02596b /MaterialsC
and the experimentally measured dispersion relationships for the nano-honeycomb structured OLEDs. Improved light out-coupling efficiency is mainly attributed to the efficient extraction of the waveguide and the surface plasmon polariton (SPP) loss modes in the devices. Particularly, most of the extracted energy is verified to be originated from the SPP loss mode in honeycomb structured OLEDs.
Cite this: J. Mater. Chem. C, 2015, 3, 1666
Origin of light manipulation in nano-honeycomb structured organic light-emitting diodes†
Xiao-Bo Shi, Min Qian, Dong-Ying Zhou, Zhao-Kui Wang* and Liang-Sheng Liao*