Effect of using ink containing polyacrylate and silicone surfactant on the inkjet printing of quantum dot films

Lin Nan,Ye Yun,Guo Qian,Yu Jinhui,Guo Tailiang 한국정보디스플레이학회 2020 Journal of information display Vol.21 No.2

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.

Wearable Electricity Generators Fabricated Utilizing Transparent Electronic Textiles Based on Polyester/Ag Nanowires/Graphene Core–Shell Nanocomposites

Wu, Chaoxing,Kim, Tae Whan,Li, Fushan,Guo, Tailiang American Chemical Society 2016 ACS NANO Vol.10 No.7

<P>The technological realization of wearable triboelectric generators is attractive because of their promising applications in wearable self-powered intelligent systems. However, the low electrical conductivity, the low electrical stability, and the low compatibility of current electronic textiles (e-textiles) and clothing restrict the comfortable and aesthetic integration of wearable generators into human clothing. Here, we present high-performance, transparent, smart e-textiles that employ commercial textiles coated with silver nanowire/graphene sheets fabricated by using a scalable, environmentally friendly, full-solution process. The smart e-textiles show superb and stable conduction of below 20 Omega/square as well as excellent flexibility, stretchability, foldability, and washability. In addition, wearable electricity-generating textiles, in which the e-textiles act as electrodes as well as wearable substrates, are presented. Because of the high compatibility of smart e-textiles and clothing, the electricity-generating textiles can be easily integrated into a glove to harvest the mechanical energy induced by the motion of the fingers. The effective output power generated by a single generator due to that motion reached as high as 7 nW/cm(2). The successful demonstration of the electricity-generating glove suggests a promising future for polyester/Ag nanowire/graphene core shell nanocomposite-based smart e-textiles for real wearable electronic systems and self-powered clothing.</P>

Wearable ultra-lightweight solar textiles based on transparent electronic fabrics

Wu, Chaoxing,Kim, Tae Whan,Guo, Tailiang,Li, Fushan Elsevier 2017 Nano energy Vol.32 No.-

<P><B>Abstract</B></P> <P>Wearable solar textiles have currently emerged as excellent candidates for potential applications in next-generation wearable functional clothing. Here, we report a wearable ultra-lightweight polymer solar textile based on transparent electronic fabrics (e-fabrics). The transparent e-fabrics with a structure of polyester/Ag nanowires/graphene core-shell have been used as anodes, as well as transparent substrates, for solar textiles. The anode buffer layer and the bulk heterojunction layer were deposited by blade-coating them onto the e-fabrics. The fabricated solar textiles show a power conversion efficiency of 2.27%, a low areal density of 5.0mg/cm<SUP>2</SUP>, good endurance against mechanical deformations, and high compatibility with clothing. These results indicate that these novel solar textiles hold potential applications in the field of wearable self-powered portable electronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wearable ultra-lightweight polymer solar textile based on transparent electronic fabrics (e-fabrics) is developed. </LI> <LI> Transparent e-fabric has been used as anodes as well as transparent substrates for solar textile. </LI> <LI> Solar textile shows a power conversion efficiency of 2.27%, good endurance against mechanical deformations, and high compatibility with clothing. </LI> <LI> Solar textile shows a low areal density of 5.0mg/cm<SUP>2</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly flexible memristive devices based on MoS₂ quantum dots sandwiched between PMSSQ layers

Perumal Veeramalai, Chandrasekar,Li, Fushan,Guo, Tailiang,Kim, Tae Whan The Royal Society of Chemistry 2019 Dalton Transactions Vol.48 No.7

<P>This paper reports a facile, cost effective method that uses an aqueous hydrothermal process for synthesizing two-dimensional molybdenum disulphide (MoS2) monolayer quantum dots (QDs) and their potential applications in flexible memristive devices. High-resolution transmission electron microscopy and atomic force microscopy images confirmed that the diameters of the synthesized MoS2 QDs with irregular shapes were in the range between 3 and 6 nm; their thicknesses were confirmed to lie between 1.0 and 0.8 nm, a clear indication that a monolayer of MoS2 QDs had been synthesized. Photoluminescence (PL) and time-resolved PL spectra of the MoS2 QDs revealed a strong emission in the blue region with a slower decay constant. Memristive devices fabricated by incorporating MoS2 QDs between poly(methylsilsesquioxane) ultrathin layers, which had been deposited on poly(ethylene terephthalate), demonstrated a high ON-OFF current ratio of ∼10<SUP>4</SUP>, stable retention, and excellent endurance in the relaxed state; these devices were also demonstrated to function properly during bending and in a bent state. The flexible memristive devices demonstrated an OFF state with a very low current of 10<SUP>−6</SUP> A. These results clearly show that ultrathin two-dimensional QDs have promising applications in high-performance flexible memristive devices.</P>

Inkjet-Printed Photodetector Arrays Based on Hybrid Perovskite CH₃NH₃PbI₃ Microwires

Liu, Yang,Li, Fushan,Perumal Veeramalai, Chandrasekar,Chen, Wei,Guo, Tailiang,Wu, Chaoxing,Kim, Tae Whan American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.13

<P>Hybrid perovskite CH3NH3PbI3 has attracted extensive research interests in optoelectronic devices in recent years. Herein an inkjet printing method has been employed to deposit a perovskite CH3NH3PbI3 layer. By choosing the proper solvent and controlling the crystal growth rate, hybrid perovskite CH3NH3PbI3 nanowires, microwires, a network, and islands were synthesized by means of inkjet printing. Electrode-gap-electrode lateral-structured photodetectors were fabricated with these different crystals, of which a hybrid perovskite microwire-based photodetector would balance the uniformity and low defects to obtain a switching ratio of 16000%, responsivity of 1.2 A/W, and normalized detectivity of 2.39 x 10(12) Jones at a light power density of 0.1 mW/cm(2). Furthermore, the hybrid perovskite microwire-based photodetector arrays were fabricated and applied in an imaging sensor, from which the clear mapping of the light source signal was successfully obtained. This work paves the way for the realization of low-cost, solution-processed, and high-performance hybrid perovskite-based photodetector arrays.</P>

Triboelectric electronic-skin based on graphene quantum dots for application in self-powered, smart, artificial fingers

Xu, Zhongwei,Wu, Chaoxing,Li, Fushan,Chen, Wei,Guo, Tailiang,Kim, Tae Whan Elsevier 2018 Nano energy Vol.49 No.-

<P><B>Abstract</B></P> <P>The development of electronic-skin (e-skin) with artificial tactile-perception is crucial for emerging artificial-intelligence systems. However, considering the relatively simple function of existing e-skins, their performances still have much room for improvement. Here, a cuttable, transparent, stretchable, and lightweight e-skin that functions on the basis of the triboelectric effect is demonstrated. Well-designed micro-gaps are introduced to make the e-skin respond sensitively to various mechanical stimulations, including pressing, stretching, folding, and twisting. Ag nanowires coated with graphene quantum dots are employed as the electrode, as well as the friction layer, to increase the sensitivity to external mechanical stimulations. Self-powered, smart, artificial fingers with tactile sensation to monitor the actions of the fingers were fabricated to demonstrate the potential application of our newly developed e-skin. The architecture and the material system of the device demonstrated in this work will promote the development of human-machine interfaces and intelligent machines.</P> <P><B>Highlights</B></P> <P> <UL> <LI> E-skins on the basis of the triboelectric effect are demonstrated. </LI> <LI> The e-skin responds sensitively to various mechanical stimulations. </LI> <LI> Graphene quantum dot-coated Ag nanowires are employed to increase the sensitivity to the mechanical stimulations. </LI> <LI> Self-powered, smart, artificial fingers based on the e-skins are demonstrated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Room temperature pH-dependent ammonia gas sensors using graphene quantum dots

Chen, Wei,Li, Fushan,Ooi, Poh Choon,Ye, Yun,Kim, Tae Whan,Guo, Tailiang Elsevier 2016 Sensors and actuators. B, Chemical Vol.222 No.-

<P><B>Abstract</B></P> <P>We report a simple solution-process route to realize ammonia (NH<SUB>3</SUB>) gas sensor based on graphene quantum dots (GQDs). Transmission electron microscopy analysis confirmed that the 8–10nm GQDs were formed from multi-walled carbon nanotubes by using ultrasonication treatment. The as-fabricated gas sensor showed promising selectivity response when expose to NH<SUB>3</SUB> ambient at room temperature. It is indicated that by adjusting the pH value of the aqueous GQDs in acidic and neutral, two types of gas sensors with contrary current responses could be obtained, which might be resulted from quantum confinement, edge effects and presence of functional groups on GQDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report an NH<SUB>3</SUB> gas sensor at room temperature based on graphene quantum dots. </LI> <LI> GQDs were formed from multi-walled carbon nanotubes by ultrasonication treatment. </LI> <LI> Adjusting the pH value of the GQDs can lead to gas sensors with different behavior. </LI> <LI> Sensing mechanism might be resulted from the unique properties of GQDs. </LI> </UL> </P>

Enhanced field emission properties of molybdenum disulphide few layer nanosheets synthesized by hydrothermal method

Veeramalai, Chandrasekar Perumal,Li, Fushan,Liu, Yang,Xu, Zhongwei,Guo, Tailiang,Kim, Tae Whan Elsevier 2016 APPLIED SURFACE SCIENCE - Vol.389 No.-

<P><B>Abstract</B></P> <P>In this work, we demonstrated the field emission properties of few layer molybdenum disulphide (MoS<SUB>2</SUB>) nanosheets synthesized by a hydrothermal method. Structural investigation indicates the as-synthesized MoS<SUB>2</SUB> layers were two dimensional few layer nanosheets with a sharp atomic edges. The field emission properties of the MoS<SUB>2</SUB> nanosheets were investigated and the results indicate that the MoS<SUB>2</SUB> nanosheets had an excellent field emission performance with turn on field of 1.0V/μm, threshold field of 2.1V/μm, and a field enhancement factor of 9880. Furthermore, the emission current shows the stability over 2h of continuous operation. The as-synthesized MoS<SUB>2</SUB> few layer nanosheets hold potential for application in next-generation field emission devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Monolayer or few layer Molepdenum disulphide nanosheets were synthesized via aqueous hydrothermal method using MoO<SUB>3</SUB> powder source. </LI> <LI> The synthesized nanosheets agglomerated while deposited on the substrates due to vanderwalls interaction between nanosheets. </LI> <LI> The superior field mission properties have been achieved for MoS<SUB>2</SUB> nanosheets attributed to the sharp edges of nanosheets. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ultrathin electronic synapse having high temporal/spatial uniformity and an Al2O3/graphene quantum dots/Al2O3 sandwich structure for neuromorphic computing

Xu, Zhongwei,Li, Fushan,Wu, Chaoxing,Ma, Fumin,Zheng, Yueting,Yang, Kaiyu,Chen, Wei,Hu, Hailong,Guo, Tailiang,Kim, Tae Whan Springer Science and Business Media LLC 2019 NPG Asia Materials Vol.11 No.-

Fluorescent Microarrays of <i>in Situ</i> Crystallized Perovskite Nanocomposites Fabricated for Patterned Applications by Using Inkjet Printing

Liu, Yang,Li, Fushan,Qiu, Lichun,Yang, Kaiyu,Li, Qianqian,Zheng, Xin,Hu, Hailong,Guo, Tailiang,Wu, Chaoxing,Kim, Tae Whan American Chemical Society 2019 ACS NANO Vol.13 No.2

<P>Perovskite materials have exhibited promising potential for universal applications including backlighting, color conversion, and anticounterfeiting labels fabricated using solution processes. However, owing to the tendency of those materials to have uncontrollable morphologies and to form large crystals, they cannot be utilized in discontinuous microminiaturization, which is crucial for practical optoelectronic applications. In this research, combining the effects of adding polyvinylpyrrolidone (PVP), precisely controlling the inkjet printing technique, and using a postprocessing procedure, we were able to fabricate <I>in situ</I> crystallized perovskite-PVP nanocomposite microarrays with perfect morphologies. The viscosity of the perovskite precursor increased with the addition of PVP, eliminating the outward capillary flow that induces the coffee-ring effect. In addition, because of the presence of metallic bonds with the C═O groups in PVP and the spatial confinement of such a polymer, we were able to fabricate regulated CsPbBr<SUB>3</SUB> nanocrystals capped with PVP and with a uniform size distribution. The as-printed patterns showed excellent homogeneity on a macroscale and high reproducibility on a microscale; furthermore, those patterns were invisible in the ambient environment, compatible with flexible substrates, and cost-efficient to produce, indicating that this technique holds promising potential for applications such as anticounterfeiting labels.</P> [FIG OMISSION]</BR>