The combination of printable supercapacitors, batteries and electronics with lithography rivaling speed could open up many new applications using very capable cheap thin films. Prices for many applications could also be driven down if these systems can produce high quality at high volumes. The high speed electronics is at room temperature
New form factors that are both very large, smaller or more flexible will be possible.
Eventually higher speed electronic printing will be possible by converting current systems to the use of multiple printing heads that print line at time and scanning down a page or page at time or eventually reel to reel printing.
Thin film supercapacitors were fabricated using printable materials to make flexible devices on plastic. The active electrodes were made from sprayed networks of single-walled carbon nanotubes (SWCNTs) serving as both electrodes and charge collectors. Using a printable aqueous gel electrolyte as well as an organic liquid electrolyte, the performances of the devices show very high energy and power densities (6 W h/kg for both electrolytes and 23 and 70 kW/kg for aqueous gel electrolyte and organic electrolyte, respectively) which is comparable to performance in other SWCNT-based supercapacitor devices fabricated using different methods. The results underline the potential of printable thin film supercapacitors. The simplified architecture and the sole use of printable materials may lead to a new class of entirely printable charge storage devices allowing for full integration with the emerging field of printed electronics.
Printable Electronics at Speeds Rivaling Computer Processors
Optomec, a leading rapid manufacturing company, has an all-printed CNT-TFT (carbon nanotube-thin film transistor) on a polyimide substrate. All the elements of the TFT are fabricated solely by using aerosol-jet printing technology without involving any photolithography fabrication steps. An ultrahigh operating frequency of over 5 GHz was demonstrated with an on-off ratio of over 100. Such an all-aerosol-jet-printed process eliminates the need for lithography, vacuum processing, and metallization procedures and thus provides a promising technology for low-cost, high-throughput fabrication of large-area high-speed flexible electronic circuits on virtually any desired flexible substrate.
Aerosol Jet printing is an additive manufacturing solution that reduces the overall size of electronic systems by using nanomaterials to produce fine feature circuitry and embedded components without the use of masks or patterns. The resulting functional electronics can have line widths and pattern features as small as 10 microns, and as large as 100 microns or more — successfully bridging the gap between existing screen-printing and thin-film lithography capabilities.
Printing TFTs on flexible substrates at room temperature offers a cost-effective way to achieve mass production of large-area electronic circuits without using special lithography equipment. This is important for many emerging applications such as flexible displays, RFID tags, electronic paper, and smart skins. The Aerosol Jet deposition process was used to completely print all four layers of the Thin Film Transistor including materials with a wide spectrum of viscosities, making it an ideal solution for this type of multi-layer device.
Dr. Mike Renn, (a co-author of the paper) states that “One of the unique benefits of the Aerosol Jet technology is that it is capable of printing TFT devices with high drain current, high on-off ratio, and low operation voltage. Additionally, Aerosol Jet systems have achieved sub-micron layer thicknesses, and less than10 micron features sizes and 5 micron registrations”.
Optomec’s Aerosol Jet systems are used in the development of next generation printable devices such as solar cells, fuel cells, embedded sensors, and more. Aerosol Jet systems use a patented process that first aerosolizes conductive and nonconductive inks or pastes and then forms an aerodynamically focused droplet stream of the material. This Direct Write capability eliminates the need for screens or stencils required by traditional contact deposition processes while also enabling much finer feature sizes than is possible with ink jet printing technology.
Optomec is the world-leading provider of additive manufacturing systems for high-performance applications in the Electronics, Aerospace & Defense, Solar, and Biomedical markets.
The TFT is in a top gated configuration. It consists of source S and drain D electrodes, a carrier transport layer based on an ultrapure, high-density >1000 CNTs/microns m^2. CNT thin film, a gate dielectric layer, and top gate electrode G. All of these TFT elements were printed on a DuPont Kapton FPC polyimide film by using an Optomec’s M3D Aerosol Jet printing system. The S and D electrodes were first printed on the Kapton FPC polyimide film using UTDAg silver nanoink from
UT-Dots, followed by the thermal annealing at 130 °C for 30 min. The width of the S and D electrodes was 50 microns, and the separation between the S and D electrodes, i.e., channel length 1, is 100 microns. An active carrier transport layer was then printed using an ultrapure, electronic grade CNT solution CJ-28 from Brewer Science, Inc.
Optomec Aerosol Jet Can Also Print Solar Cells with 20.3% efficiency
The Aerosol Jet printed solar cells achieved efficiencies of over 20% when combined with Light Induced Plating (LIP) and Annealing, versus an average efficiency for screen-printed mono-crystalline front junction silicon solar cells in the range of 16–18%. The narrower, higher integrity collector lines produced by Aerosol Jet deposition systems have higher conductivity and a lower shadowing effect, thereby increasing cell efficiency. In addition, because the process is non-contact, Optomec’s Aerosol Jet system can print on thinner wafers and with less breakage than screen- printing.
Aerojet Process and Printer