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Inkjet printing a small-molecule binary emitting layer for organic light-emitting diodes
摘要： For inkjet-printed organic light-emitting diodes, it is critical to obtain a homogeneous small molecular-based emitting film. In contrast to the conventional strategy of utilizing mixed solvents, we have successfully inkjet printed a binary electrophosphorescent emitter with a single solvent. The binary emitter consists of a new host material of 3-(3,6-di-t-butylcarbazol-9-yl)-3'-(2-(4-t-butylphenyl)benzoimidazol-1-yl)-[1,1'-biphenyl], and an iridium complex dopant of bis(2-methyldibenzo[f,h]quinoxaline)(acetylacetonate)- iridium(III) (Ir(MDQ)2(acac)). Compatible with Ir(MDQ)2(acac), the newly developed host is highly soluble and amorphous with a glass transition temperature of 137 oC upon cooling from the melt. The inkjet printability and film morphology of the emitting layer are strongly dependent both on substrates and the solvents. With the o-dichlorobenzene (o-DCB) as the single solvent, and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4?-(N-(p-butylphenyl))diphenylamine)] (TFB) as the hole transporting layer, a uniform emitter film morphology without any coffee ring is obtained. The phosphorescent OLEDs with the inkjet-printed emitter yields a maximum current efficiency of 17.89 cd/A, comparable to that of the Ir(MDQ)2(acac)?based OLEDs with spin-cast emitter.
关键词： Dewetting,Coffee ring,Inkjet printing,Phosphorescent OLEDs,Small molecules
更新于2025-09-23 15:21:01
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Edge Enriched Self-assembly of Au Nanoparticles: Coffee-Ring Effect during Microcontact Printing via Agarose Stamps
摘要： Amino functionalized surfaces were selectively modified via the combination of a wet agarose stamping technique and microcontact printing technique. Because of the specific reaction environments and diffusion of HNO2 confined in agarose stamp, the reaction of amino groups in the edge of the strip pattern was much more intense than other areas. The modified amino groups in the edge areas show higher affinity to Au-NPs than other areas, consequently, edge enriched Au-NPs patterns were observed after the self-assembly of Au-NPs. A “cylindrical droplet” model, in a manner analogous to coffee-ring effect, was proposed to describe the diffusion of HNO2 from the bulk to the edge in agarose stamp. By using such density varied Au-NPs patterns as templates for the growth of ZnO nanorods, we observed high density of Au-NPs resulting in high density and highly (001) oriented ZnO nanorods. In contrast, sparse and non-oriented ZnO nanorods were grew on low density of Au-NPs areas. Our findings might open new routes for the fabrication of gradient patterns and extend applications of Au-NPs patterns in surface enhanced Raman scattering and catalysis.
关键词： coffee-ring effect,gradient patterns,microcontact printing,agarose stamp,self-assembly
更新于2025-09-23 15:21:01
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Effect of using ink containing polyacrylate and silicone surfactant on the inkjet printing of quantum dot films
摘要： For device printing, it is important for uniform films to be printed because the morphology of the film affects the performance of the device in inkjet printing. In this study, to prepare stable and well-dispersed ink, polyacrylate and silicone surfactant BD-3033H were added to ink. Then a uniform quantum dot (QD) film was obtained by optimizing the polyacrylate and silicone surfactant contents of the ink as well as the substrate temperature. The change of the polyacrylate structure from a curly chain structure to a three-dimensional network structure blocked the outward flow of QDs. Silicone surfactant BD-3033H caused Marangoni flow and made the QDs flow inward. When the substrate temperature was increased, the solvent evaporation rate was accelerated, the contact line was pinned, and the outward flow was enhanced, which changed the film structure from convex to flat. Finally, when the polyacrylate content was 12 wt%, the silicone surfactant BD-3033H content was 0.10 wt%, the substrate temperature was 40°C, and the coffee ring effect was eliminated. A uniform QD film was printed, providing a technical guarantee for the fabrication of QD devices in the future.
关键词： polyacrylate,coffee ring,Quantum dot film,silicone surfactant,inkjet printing
更新于2025-09-16 10:30:52
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Designing of low-cost, eco-friendly, and versatile photosensitive composites / inks based on carboxyl-terminated quantum dots and reactive prepolymers in a mixed solvent: Suppression of the coffee-ring strain and aggregation
摘要： Today, solution processable quantum dots (QDs) are receiving great attention as photon down converters for various photoluminescent device architectures such as next-generation solid-state lighting (SSL) and micro-light emitting diodes (LEDs). However, fabrication of QDs in commercial applications is still limited due to the lack of suitable QD composites that can address current technical issues such as polymer induced QD aggregation, ring-like deformation (called the coffee-ring effect), and so on. In the present study, carboxyl-terminated QD based composites are proposed as a potential solution. As a ligand molecule for model carboxyl-terminated QDs, 3-mercaptosuccinic acid (MSA) was used and MSA-capped QDs (MSA-QDs) showed excellent dispersion properties (up to 70%, by weight) in industrial solvents such as propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA). For photosensitive composites (e.g., photoresist, ink), photoreactive bisphenol A-based epoxy resins (e.g., SU-8) and cardo-based acrylic resins as binders are studied under co-solvent systems. As a result, the bisphenol A-based composite (e.g., SU-8/MSA-QD composites) were found to exhibit good QD uniformity in the matrix. In addition, corresponding resin-based QD inks are shown to significantly suppress ring-like deformation in droplets when cyclopentanone (CP) is used as co-solvent.
关键词： Carboxyl-terminated quantum dots,Suppression of coffee-ring effect,Photosensitive composites
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 2nd International Conference on Electronics Technology (ICET) - Chengdu, China (2019.5.10-2019.5.13)] 2019 IEEE 2nd International Conference on Electronics Technology (ICET) - Efficient Top-emitting Quantum Dot Light Emitting Diodes via Inkjet Printing
摘要： In this work, we report inkjet-printed top-emitting (TE) quantum dot light emitting diodes (QLEDs) for achieving high-resolution QLED displays. At the luminance of 1000 cd/m2, the TE devices exhibit a current efficiency of 5.90 cd/A which is 2.7-fold higher than 2.18 cd/A of the conventional bottom-emitting (BE) devices. The significant enhancement is owing to the well-controlled cavity length which is easy for inkjet printing.
关键词： QLEDs,top-emitting structures,inkjet printing,coffee ring,Quantum dot
更新于2025-09-12 10:27:22
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Optimization of dispersant-free colloidal ink droplets for inkjet patterning without the coffee-ring effect using 1-octanethiol-coated copper nano-ink with a Standard Clean-1-treated substrate
摘要： Inkjet-printed patterns and droplets were formed by the inkjet printing method on a Standard Clean-1 (SC-1)-treated substrate using anti-oxidized copper nano-ink. The hydrophobicity of the substrate increased after the SC-1 treatment. Copper nanoparticles were coated with 1-octanethiol vapors via a dry coating method to produce anti-oxidized nanoparticles, which were dispersed in a solvent to form a nano-ink. Droplets of the 1-octanethiol-coated copper nano-ink at 50 wt% concentration had a uniform morphology when printed on the SC-1-treated glass substrate. The minimum printed pattern line width was 55 μm on the SC-1-treated glass and had a resistivity of 1.73 × 10–7 ?·m. This resistivity was 4.3-times lower than that of the untreated substrate. Moreover, the pattern printed using the nano-ink made with 1-octanethiol-coated copper nanoparticles showed good adhesion and provided approximately 2.1-times lower resistivity. The dispersion of the nanoparticles within the droplet was more hydrophobic and formed uniform inkjet-printed patterns that had lower resistivity compared with those made with the uncoated nanoparticle-containing ink.
关键词： SC-1 treatment,Coffee-ring effect,1-Octanethiol-coated copper nano-ink,Inkjet printing,Resistivity
更新于2025-09-10 09:29:36
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Visualized Quantitation of Trace Nucleic Acids Based on Coffee-Ring Effect on Colloid-Crystal Substrate
摘要： We report a visualized quantitative detection method for nucleic-acid amplification tests based on coffee-ring effect on colloid-crystal substrate. The solution for loop-mediated isothermal amplification (LAMP) of DNA is dropcast on a colloid-crystal surface. After complete drying, a coffee ring containing the LAMP byproduct (i.e. magnesium pyrophosphate) is formed, and it is found that the width of the coffee ring is linearly correlated to the logarithm of the original DNA concentration before the isothermal amplification. Importantly, compared with other substrates, we found that the colloidal-crystal substrate is an appropriate substrate for carrying out the assay of high sensitivity. Based on these findings, we develop a coffee ring-based assay for quantitative readout of trace DNA in sample. The assay requires 0.50 μL sample and is completed in 5 min in a homemade chamber with constant humidity. Semi-quantitative detection of trace DNA is performed using naked eyes. With the use of a smartphone, the DNA in a sample can be quantitatively detected with a limit-of-detection of 20 copies.
关键词： nucleic-acid amplification tests,colloid-crystal substrate,LAMP,quantitative detection,coffee-ring effect
更新于2025-09-10 09:29:36