Roll‐to‐Roll Cohesive, Coated, Flexible, High‐Efficiency Polymer Light‐Emitting Diodes Utilizing ITO‐Free Polymer Anodes

This paper reports solution‐processed, high‐efficiency polymer light‐emitting diodes fabricated by a new type of roll‐to‐roll coating method under ambient air conditions. A noble roll‐to‐roll cohesive coating system utilizes only natural gravity and the surface tension of the solution to flow out from the capillary to the surface of the substrate. Because this mechanism uses a minimally cohesive solution, the roll‐to‐roll cohesive coating can effectively realize an ultra‐thin film thickness for the electron injection layer. In addition, the roll‐to‐roll cohesive coating enables the fabrication of a thicker polymer anode film more than 250 nm at one time by modification of the surface energy and without wasting the solution. It is observed that the standard sheet resistance deviation of the polymer anode is only 2.32 Ω/□ over 50 000 bending cycles. The standard sheet resistance deviation of the polymer anode in the different bending angles (0 to 180°) is 0.313 Ω/□, but the case of the ITO‐PET is 104.93 Ω/□. The average surface roughness of the polymer anode measured by atomic force microscopy is only 1.06 nm. Because the surface of the polymer anode has a better quality, the leakage current of the polymer light‐emitting diodes (PLEDs) using the polymer anode is much lower than that using the ITO‐PET substrate. The luminous power efficiency of the two devices is 4.13 lm/W for the polymer anode and 3.21 lm/W for the ITO‐PET. Consequently, the PLEDs made by using the polymer anode exhibited 28% enhanced performance because the polymer anode represents not only a higher transparency than the ITO‐PET in the wavelength of 560 nm but also greatly reduced roughness. The optimized the maximum current efficiency and power efficiency of the device show around 6.1 cd/A and 5.1 lm/W, respectively, which is comparable to the case of using the ITO‐glass. This roll‐to‐roll cohesive coating method utilizes only the natural gravity and cohesive force of the solutions. The coating film thickness can be effectively reduced for the ultra‐thin electron injection layer. Furthermore, the roll‐to‐roll cohesive coating enables the fabrication of a thicker polymer anode more than 250 nm at one time by modification of the surface energy and without wasting the solution.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102247/1/smll_201300382_sm_suppl.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102247/2/4036_ftp.pd

Super Black Coating on the Commercial Black Anodized Al(6061) by Direct and Scalable CVD–Growth of Carbon Nanofibers

Abstract Using carbon‐based super black coatings on optical devices can achieve superior stray light suppression for applications in astronomy. For the first time, the work presents carbon nanofiber‐based black coating on commercial anodized Al(6061), which facilitates the development of a highly effective route to directly integrate the carbon‐based material on the common substrate for optical baffles. The scalable and available structural engineering effect is synergized with the anodized Al(6061) coating with black dye composed of nickel catalyst and the intrinsic broadband light absorption of the CVD‐grown carbon material to ultimately achieve a superior broadband light absorber. Nickel catalysts embedded in anodized Al(6061) offer a practical pathway for carbon nanofiber growth through CVD without additional stacked catalysts. The CVD‐growing mechanism and CNF nanostructures are demonstrated through TEM and EDS element mapping, SEM, and Raman spectroscopy. CNF‐grown Al(6061) substrates offer above 99% broadband light absorption and low light reflectance below 1% in UV–vis–NIR and mid–IR ranges. This facile approach has been useful for super black coating on Al(6061)‐based complicated sculptures, such as concave substrate and an optical baffle. These results have demonstrated a facile method that can significantly impact the industrial scaling‐up of high‐quality, super‐black coating on spaceborne devices

A PANAS Structure Analysis: On the Validity of a Bifactor Model in Korean College Students

The purpose of this study was to determine the best model fit among the six models in the Korean version of Positive and Negative Affect Schedule (K-PANAS). Therefore, this study compared and analyzed the dimensional structure of this schedule for Korean college students. Specifically, the model fitness of six models, which are under debate, were compared: a single model for K-PANAS, a two-factor model (PA&NA) without any factor correlation, a three-factor model (PA, NA-Afraid, NA-Upset), a two-factor bifactor model, a three-factor bifactor model, and a three-factor bifactor model with error correlation. A total of 875 samples were analyzed, and the results show that best model fit is the three-factor bifactor model with error correlation. We named the general factor of the bifactor model “activation (or arousal).” This findings of this study will provide a richer explanation of emotions for researchers analyzing emotional activation (or arousal), a general factor of emotion, PA, and NA future studies that use PANAS

A PANAS Structure Analysis: On the Validity of a Bifactor Model in Korean College Students

The purpose of this study was to determine the best model fit among the six models in the Korean version of Positive and Negative Affect Schedule (K-PANAS). Therefore, this study compared and analyzed the dimensional structure of this schedule for Korean college students. Specifically, the model fitness of six models, which are under debate, were compared: a single model for K-PANAS, a two-factor model (PA&NA) without any factor correlation, a three-factor model (PA, NA-Afraid, NA-Upset), a two-factor bifactor model, a three-factor bifactor model, and a three-factor bifactor model with error correlation. A total of 875 samples were analyzed, and the results show that best model fit is the three-factor bifactor model with error correlation. We named the general factor of the bifactor model “activation (or arousal).” This findings of this study will provide a richer explanation of emotions for researchers analyzing emotional activation (or arousal), a general factor of emotion, PA, and NA future studies that use PANAS

Solution-processable electrode-material embedding in dynamically inscribed nanopatterns (SPEEDIN) for continuous fabrication of durable flexible devices

A facile and scalable lithography-free fabrication technique, named solution-processable electrode-material embedding in dynamically inscribed nanopatterns (SPEEDIN), is developed to produce highly durable electronics. SPEEDIN uniquely utilizes a single continuous flow-line manufacturing process comprised of dynamic nanoinscribing and metal nanoparticle solution coating with selective embedding. Nano- and/or micro-trenches are inscribed into arbitrary polymers, and then an Ag nanoparticle solution is dispersed, soft-baked, doctor-bladed, and hard-baked to embed Ag micro- and nanowire structures into the trenches. Compared to lithographically embossed metal structures, the embedded SPEEDIN architectures can achieve higher durability with comparable optical and electrical properties and are robust and power-efficient even under extreme stresses such as scratching and bending. As one tangible application of SPEEDIN, we demonstrate a flexible metal electrode that can operate at 5 V at temperatures up to 300 degrees C even under the influence of harsh external stimuli. SPEEDIN can be applied to the scalable fabrication of diverse flexible devices that are reliable for heavy-duty operation in harsh environments involving high temperatures, mechanical deformations, and chemical hazards.11Nsciescopu

A photonic sintering derived Ag flake/nanoparticle-based highly sensitive stretchable strain sensor for human motion monitoring

Recently, the demand for stretchable strain sensors used for detecting human motion is rapidly increasing. This paper proposes high-performance strain sensors based on Ag flake/Ag nanocrystal (NC) hybrid materials incorporated into a polydimethylsiloxane (PDMS) elastomer. The addition of Ag NCs into an Ag flake network enhances the electrical conductivity and sensitivity of the strain sensors. The intense localized heating of Ag flakes/NCs is induced by intense pulsed light (IPL) irradiation, to achieve efficient sintering of the Ag NCs within a second, without damaging the PDMS matrix. This leads to significant improvement in the sensor sensitivity. Our strain sensors are highly stretchable (maximum strain = 80%) and sensitive (gauge factor = 7.1) with high mechanical stability over 10 000 stretching cycles under 50% strain. For practical demonstration, the fabrication of a smart glove for detecting the motions of fingers and a sports band for measuring the applied arm strength is also presented. This study provides an effective method for fabricating elastomer-based high-performance stretchable electronics. © 2018 The Royal Society of Chemistry.1

Rapid and conformal coating of polymer resins by airbrushing for continuous and high-speed roll-to-roll nanopatterning: parametric quality controls and extended applications

Abstract We present a facile and scalable coating method based on controlled airbrushing, which is suitable for conformal resin coating in continuous roll-to-roll (R2R) nanoimprint lithography (NIL) process. By controlling the concentration of UV-curable polymeric resin with mixing the volatile solvent and its airbrushing time, the coated resin film thickness can be readily tuned. After R2R NIL using a flexible nanoscale line pattern (nanograting) mold is conducted upon the airbrushed resin film, a large-area uniform nanograting pattern is fabricated with controlled residual layer thickness (RLT) based on the initial film thickness. We investigate the faithful airbrushing condition that can reliably create the uniform thin films as well as various nanopatterns with controlled morphologies. Using more diluted resin and shorter airbrushing time can reduce the RLTs favourably for many applications, yet is apt to induce the nanoscale pores and discontinued lines. We also discuss how to further improve the quality and scalability of resin airbrushing and its potential applications particularly requiring high-speed and conformal coating on highly topographic and flexible surfaces