Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Formation of organic thin-film transistors through room-temperature printing


Japanese researchers have established a process for forming organic thin-film transistors (TFTs), conducting the entire printing process at room temperature under ambient atmospheric conditions.

Printed electronics, the field in which electronic devices are produced by printing functional materials in ink form without the need for large and expensive manufacturing equipment, has been drawing attention in recent years as a new technology for low-cost, large-area fabrication of semiconductor devices.

Ambient conductive metal nanoparticles and an organic transistor created in this research

(a) Schematic and a scanning electron micrograph of ambient conductive metal nanoparticles. By using conductive aromatic ligands, the nanoparticles exhibit conductivity matching that of metal by room-temperature drying.

(b) Schematic of an organic TFT formed by a room-temperature printing process. Since all layers of the TFT can be formed without raising the temperature by even 1°C, non-heat-resistant materials can also be used as substrates. It also exhibits extremely high mobility compared to conventional organic TFTs.

By using plastic and other flexible substrates, the technology is expected to open paths for the mass production of devices by roll-to-roll processing or for new applications such as wearable devices. However, conventional printed electronics require many high-temperature processes ranging from 100 to 200°C.

Because plastic substrates such as PET film generally have low heat resistance, there have been calls for the development of a low-temperature printing process that involves no high-temperature processes and that is applicable to a wide range of materials. However, such a process has not been realized to date.

In this research, the team established "room-temperature-printed electronics" by which electronics devices can be manufactured by conducting all of the printing processes at room temperature under ambient atmospheric conditions, without raising the temperature by even 1°C. Conventional printed electronics have mainly required high-temperature processes in order to sinter metal nanoparticle ink to be used as electrodes.

Since conventional metal nanoparticles have used insulating materials as ligands for dispersing the nanoparticles in the ink, the nanoparticles have needed to be sintered in order to obtain a conductive metal film.

In this research, the team succeeded in forming a metal film without post-coating sintering, by using conductive aromatic molecules as ligands of metal nanoparticles. The thin film obtained has achieved a resistivity of 9 × 10-6 Ω cm. In addition, by forming microscopic hydrophilic/hydrophobic patterns on the surface, the team patterned ambient conductive metal nanoparticles and organic semiconductors by a room-temperature process, and made organic thin-film transistors by forming all of the source and drain electrodes, organic semiconductors and gate electrodes by room-temperature printing.

Organic TFTs formed on a plastic substrate and a paper substrate respectively indicated an average mobility of 7.9 and 2.5 cm2V-1 s-1. This value far exceeds the average mobility of amorphous silicon TFTs at 0.5 cm2 V-1s-1 and almost matches the mobility of mass-produced IGZO TFTs (up to 10 cm2 V-1 s-1).

When manufacturing displays, etc. by printed electronics, circuits need to be printed on flexible substrates at a positional accuracy greater than several microns. Flexible plastic and paper substrates, which are weak against heat, became deformed or distorted under the conventional processing temperatures, leading to compromised accuracy.

By conducting all of the manufacturing processes at room temperature, it will be possible to completely control the heat deformation of substrates and to print micro circuits at high accuracy. Furthermore, the production processes at room temperature under ambient atmospheric conditions would, in principle, enable the production of electronic devices on the surface of materials that are extremely weak against environmental changes, such as biomaterials. This achievement is expected to lead to applications in diverse fields including health care and bioelectronics.

These research results will be published in the journal, Advanced Functional Materials, in the near future.

Mikiko Tanifuji | Research SEA News
Further information:

More articles from Materials Sciences:

nachricht Coming to a monitor near you: A defect-free, molecule-thick film
27.11.2015 | University of California - Berkeley

nachricht Controlling Electromagnetic Radiation by Graphene
27.11.2015 | Universität Augsburg

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate study finds evidence of global shift in the 1980s

Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fuelled by anthropogenic warming and a volcanic eruption, according to new research published this week.

Scientists say that a major step change, or ‘regime shift’, in the Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from...

Im Focus: Innovative Photovoltaics – from the Lab to the Façade

Fraunhofer ISE Demonstrates New Cell and Module Technologies on its Outer Building Façade

The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...

Im Focus: Lactate for Brain Energy

Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.

In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...

Im Focus: Laser process simulation available as app for first time

In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.

Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...

Im Focus: Quantum Simulation: A Better Understanding of Magnetism

Heidelberg physicists use ultracold atoms to imitate the behaviour of electrons in a solid

Researchers at Heidelberg University have devised a new way to study the phenomenon of magnetism. Using ultracold atoms at near absolute zero, they prepared a...

All Focus news of the innovation-report >>>



Event News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

Gluten oder nicht Gluten? Überempfindlichkeit auf Weizen kann unterschiedliche Ursachen haben

17.11.2015 | Event News

Art Collection Deutsche Börse zeigt Ausstellung „Traces of Disorder“

21.10.2015 | Event News

Latest News

Siemens to supply 126 megawatts to onshore wind power plants in Scotland

27.11.2015 | Press release

Two decades of training students and experts in tracking infectious disease

27.11.2015 | Life Sciences

Coming to a monitor near you: A defect-free, molecule-thick film

27.11.2015 | Materials Sciences

More VideoLinks >>>