Jolke Perelaer

Printed electronics: the challenges involved in printing devices, interconnects, and contacts based on inorganic materials

Printed electronics represent an emerging area of research that promises large markets due to the ability to bypass traditional expensive and inflexible silicon-based electronics to fabricate a variety of devices on flexible substrates using high-throughput printing approaches. This article presents a summary of work to date in the field of printed electronics and the materials chemistry involved. In particular, the focus is upon the use of metal- and metal oxide-containing inks in the preparation of contacts and interconnects. The review discusses the challenges associated with processing these types of inks and ways to successfully obtain the desired features.

Inkjet-printed silver tracks : low temperature curing and thermal stability investigation

In this contribution the curing behavior and conductivity development of several commercially available silver inks is discussed. In addition, the preparation and characterization of a silver particle ink that shows a curing temperature as low as 80 °C is described. Good to excellent conductivity values of 5 to 56% of bulk silver have been reached by using a very small amount of organic additives without any strong adsorbing groups such as amines, amides or mercapto groups. This low curing temperature opens new routes to produce conductive features on polymeric foils that have a low Tg, like PET. Furthermore, the temperature stability of silver tracks, prepared by inkjet printing different colloidal silver suspensions, was investigated. Hereto, the resistance was on-line measured during heating of the silver tracks, from room temperature to 650 °C.

One-step inkjet printing of conductive silver tracks on polymer substrates

A one-step process to fabricate conductive features on flexible polymer substrates by inkjet printing an organometallic silver ink directly onto a substrate that is heated to 130 degrees C is presented. This process led to the immediate sintering of the printed features. The samples were left for 5 min at elevated temperature, which resulted in conductive silver features with a resistivity of eight times the bulk silver value. The combination of this ink and the simultaneous printing/sintering process opens up routes for the direct fabrication of conductive features on common polymer substrates that could be applied, for example, in roll-to-roll production of flexible microelectronic systems.

Microwave flash sintering of inkjet-printed silver tracks on polymer substrates

Microwave flash sintering of inkjet printed colloidal silver dispersions on thin polymer substrates was studied as a function of the antenna area and initial resistance. The presence of conductive antennae promotes nanoparticle sintering in predried ink lines. For dried nanoparticle inks connected to antennae, sintering times of 1 s are sufficient to obtain pronounced nanoparticle sintering and conductivities between 10 and 34% compared to bulk silver.

Argon plasma sintering of inkjet printed silver tracks on polymer substrates

An alternative and selective sintering method for the fabrication of conductive silver tracks on common polymer substrates is presented, by exposure to low-pressure argon plasma. Inkjet printing has been used to pattern a silver nanoparticle ink. This resulted in conductive features with a resistivity less than one order of magnitude higher than the bulk value of silver without affecting the polymer substrate. This process may be employed in the production of conductive features with low material usage on common polymer substrates in, for example, printed electronics.

Roll‐to‐Roll Compatible Sintering of Inkjet Printed Features by Photonic and Microwave Exposure: From Non‐Conductive Ink to 40% Bulk Silver Conductivity in Less Than 15 Seconds

A combination of photonic and microwave flash exposure is used to sinter inkjet printed silver nanoparticles. This approach leads to conductive features on polymer substrates in short times that are compatible with roll-to-roll production. The sequential process of sintering the as-printed features revealed a final conductivity of 40% of bulk silver, in less than 15 seconds.

Inkjet printing of organic electronics – comparison of deposition techniques and state-of-the-art developments

Inkjet printing represents a solution dispensing technique that is characterized by its non-contact, material-efficient and reproducible processing. This critical review discusses the use of inkjet printing for organic electronics with a focus on the applicability as well as the drying behavior. The nascent inkjet printing technique is compared to commonly used solution deposition methods, like spin-coating and doctor blading. Basic drying principles of inkjet printed features are understood and fundamental correlations between processing properties and film characteristics can be drawn. It is, however, a long way to gain a full understanding of the complete drying process, since the process conditions as well as the ink properties correlate in a complex relation with the final device properties. Nevertheless, inkjet printing has the potential to evolve as one of the most promising film preparation techniques in the future and has already been applied successfully in combinatorial screening workflows and for the preparation of organic solar cell devices.

Geometric control of inkjet printed features using a gelating polymer

When an inkjet printed feature is formed, the behaviour of the ink on the substrate is of great importance. In order to investigate the possibility of increased control over the as-printed feature on a substrate, a TiO2 ink was formulated that gels above a certain temperature. The TiO2 particles in the ink are colloidally stabilised by an adsorbed layer of poly(vinyl methyl ether)-block-poly(vinyloxy-4-butyric acid) diblock copolymer. The thermal gelation, at about 37 °C, is due to the limited solubility of the poly(vinyl methyl ether) buoyant block in the continuous medium of the ink. Drops and lines with improved morphological control and resolution were achieved using the thermal gelation effect. Lines printed using this approach did not display deviations at their starts and ends; and bulges in the line could be avoided. Finally, defect-free straight lines could be printed on very hydrophobic surfaces, which is impossible with regular inks due to the de-wetting nature of such substrates.

Progress of alternative sintering approaches of inkjet-printed metal inks and their application for manufacturing of flexible electronic devices

Well-defined high resolution structures with excellent electrical conductivities are key components of almost every electronic device. Producing these by printing metal based conductive inks on polymer foils represents an important step forward towards the manufacturing of plastic electronic products on an industrial scale. The development of fast, efficient and inexpensive post-deposition sintering technologies for these materials is an important processing step to make this approach commercially viable. This review discusses the advances in alternative sintering approaches for conductive, metal containing inks, which can be processed by inkjet-printing processes. Each sintering approach is examined regarding its mechanism, its compatibility with commonly used materials in the field of flexible electronics, its compatibility with high-throughput manufacturing processes and its applicability to the production of flexible electronic devices.

Plasma and Microwave Flash Sintering of a Tailored Silver Nanoparticle Ink, Yielding 60% Bulk Conductivity on Cost‐Effective Polymer Foils

A combination of plasma and microwave flash sintering is used to sinter an inkjet-printed and tailored silver nanoparticle formulation. By using two sintering techniques sequentially, the obtained conductivity is 60%, while keeping the processing temperature well below the glass transition temperature (T(g)) of the used polymer substrate. This approach leads to highly conductive features on cost-effective polymer substrates in relatively short times, which are compatible with roll-to-roll (R2R) production. An electroluminescence device is prepared as an example.