Printed copper-nanoplate conductor for electro-magnetic interference

As one of the conductive ink materials with high electric conductivity, elemental copper (Cu) based nanocrystals promise for printable electronics. Here, single crystalline Cu nanoplates were synthesized using a facile hydrothermal method. Size engineering of Cu nanoplates can be rationalized by using the LaMer model and the versatile Cu conductive ink materials are suitable for different printing technologies. The printed Cu traces show high electric conductivity of 6 MS/m, exhibiting electro-magnetic interference shielding efficiency value of 75 dB at an average thicknesses of 11 μm. Together with flexible alumina ceramic aerogel substrates, it kept 87% conductivity at the environmental temperature of 400 ℃, demonstrating the potential of Cu conductive ink for high-temperature printable electronics applications.

High-performance hysteresis-free perovskite transistors through anion engineering

Despite the impressive development of metal halide perovskites in diverse optoelectronics, progress on high-performance transistors employing state-of-the-art perovskite channels has been limited owing to ion migration and large organic spacer isolation. Herein, we report high-performance and hysteresis-free p-channel perovskite thin-film transistors (TFTs) based on methylammonium tin iodide (MASnI3) and rationalise the effects of halide (I/Br/Cl) anion engineering on crystallinity enhancement and vacancy suppression, realising a high hole mobility of 20 cm2 V−1 s−1, current on/off ratio exceeding 107, and threshold voltage of 0 V with high operational stability and reproducibility. We reveal ion migration has a negligible contribution to the hysteresis of Sn-based perovskite TFTs; instead, minority carrier trapping is the primary cause. Finally, we integrate the perovskite TFTs with commercialised n-channel indium gallium zinc oxide TFTs on a single chip to construct high-gain complementary inverters, facilitating the development of halide perovskite semiconductors for printable electronics and circuits.

Characterizing the Conductivity of Aerosol Jet Printed Silver Features on Glass

Aerosol Jet Printing shows a lot of promise for the future of printable electronics. It is compatible with a wide range of materials and can be printed on nearly any type of surface features because of its 3–5 mm standoff distance from the substrate. However, nearly all materials printed require some form of post-sintering processing to reduce the electrical resistance. Many companies develop these materials, but only provide a narrow range of post processing results to demonstrate the achievable conductivity values. In this paper, a design of experiment (DOE) is presented that demonstrates a way to characterize any material for Aerosol Jet Printing during and after post sintering processing by measuring conductivity with different time and temperature values. From these results, a linear regression model can be made to develop an equation that predicts conductivity at a given time-temperature value. This paper applies this method to Clariant Ag ink and sinters silver pads in an oven. A linear regression model is successfully developed that fits the data very well. From this model, an equation is derived to predict the conductivity of the Clariant Ag ink for any time-temperature value. Although only demonstrated with an oven and one type of ink, this method of experimentation and model development can be done with any material and any post processing method.

Sulvanites: The Promise at the Nanoscale

The class of ternary copper chalcogenides Cu3MX4 (M = V, Nb, Ta; X = S, Se, Te), also known as the sulvanite family, has attracted attention in the past decade as featuring promising materials for optoelectronic devices, including solar photovoltaics. Experimental and theoretical studies of these semiconductors have provided much insight into their properties, both in bulk and at the nanoscale. The recent realization of sulvanites at the nanoscale opens new avenues for the compounds toward printable electronics. This review is aimed at the consideration of synthesis methods, relevant properties and the recent developments of the most important sulvanites.

Anilox Cell Geometries For Printable Electronics and Flexible Packaging

Flexography is a major high-volume printing process used extensively for flexible packaging. The heart of flexographic press is the anilox roll, which meters the flow of ink to the image carrier (plate) by virtue of the engraved cells on the surface. The anilox was original engraved mechanically using a stylus to peck at the surface. This limited the size and profile of the engraved cells. However, laser engraving has enabled much more control with a variety of shapes and aspect ratios. Much has been claimed by the manufacturers for these new designs – improved ink transfer, higher volumes of ink transfer and better half tone reproduction – on the basis of industrial field trials. The objective of the research reported in this thesis has been to quantify the ink release from the anilox to the plate for both traditional cell profiles and the open channel designs.Previously, the ink release was mostly determined by examining the optical density of the print products. The optical density is a qualitative indicator of the ink release from anilox cells. These studies were limited to closed anilox cells with a low ink viscosity, as typically used for graphic prints. This study explores an extended range of anilox cell shapes, including open channel geometries, and the ink viscosities. The ink released from the anilox cells has been be directly measuring and quantified.Experiments were performed printing directly to glass and on flexible packaging at a commercial printers to establish the current industry position. A laboratory scale printability tester was then used to study ink release using three inks: UV Cyan, Carbon and Silver. These represented a link to the graphic experiments in previous published studies, while the Carbon and Silver were highly viscoelastic functional inks used in printed electronics. Four cell geometries were used: laser engraved closed cells, extended hexagonal and wavy channels together with mechanically engraved conventional closed pyramid cells. The laser engraved anilox afforded the opportunity to vary key parameters of cell width, depth, profile and volume. A brief exploration of print speed was also undertaken with exemplar anilox of each cell type. The main study considered ink transfer to a 100% solid plate, as this would allow the ink release to be studied without influence of the plate distorting into the cells thereby extracting more ink. A limited study was then undertaken with a half tone plate to establish the impacted on ink transfer.The amount of ink transferred was highly dependent on the absolute volume of cells, i.e. the amount of ink available on the anilox. The anilox cells with wider, shallower and smaller depth-to-width ratio released a higher proportion of the ink. The ink’s physical characteristics of viscoelasticity and extensional viscosity also determine the proportion of ink transferred.The anilox hexagonal closed cells (typically used in the flexographic printing process) performed best with the low viscosity ink. The information gaining from this study would aid in the design of anilox cell geometries and development of ink characteristics to enhance its capability for functional print applications such as printable electronics. The anilox wavy channels released the greatest proportion of the ink with high viscosity, elastic modulus, and filament breakup time. The anilox wavy channel has the potential to be used for the functional print as it increased the release of paste-like ink. Additionally, it improved the ink lay-down. The anilox engraving technique affected the ink release. The anilox cells, which were engraved by the laser technique, gave greater ink release comparing to the anilox cells, which were engraved by the mechanically engraving technique. The increase of the dot coverage increased the ink release out of the anilox cells because of the increase of the receiving area. However, the increase of the ink release plateaued after the dot coverage of 50% for UV Silver because of its large filament breakup time.The characteristics of ink influenced the ink release out of the anilox cells. Unlike previous work which examined only the ink viscosity, this studied included ink elastic modulus and filament breakup. The ink with high viscosity and elastic modulus, but small filament breakup time gave greatest ink release for all anilox shapes.When the printing speed increased, it decreased the ink release due to two factors; reduction of engagement time between the anilox cells and the plate (reducing time for ink to transfer) and enlargement of the filament extension rate (reducing the amount of ink transfer). The decrease of ink release was affected by the ink characteristics and the anilox cells shapes. The decrease of ink release was significant when UV Cyan ink (small viscosity and elastic modulus) was used with the anilox open cells and wavy channels. Contrarily, the decrease of ink release was insignificant when UV Carbon and Silver inks (large viscosity and elastic modulus) was used with the anilox open cells and wavy channels.The experimental data was analysed and the critical parameters in releasing the ink of the anilox cells were identified. The depth of anilox cell was the most critical parameter; the shallower cell depth released a higher proportion of the ink. The ratio of depth-to-width was the second most important parameter in determining the ink release. The smaller depth-to-width ratio released more ink. The width of anilox cell could not be used as a parameter predicting the ink release because the wider anilox cell did not always release the higher proportion of the ink.

High-resolution and scalable printing of highly conductive PEDOT:PSS for printable electronics

Topographical discontinuous dewetting (TDD) and liquid bridge transfer (LBT) was used for submicron resolution, R2R-compatible, high thickness, low line edge roughness patterning of PEDOT:PSS. High conductivities up to ∼2590 S cm−1 were achieved.