By Nick Gilbert
Printed thin film transistor is the key building block that connects all printed electronic components, which include sensors, memories, antennas, batteries, and much more. It is an essential device as it enables logic, and thus data processing. However, in spite of years of advancement, printed transistors are not yet commercially feasible.
IDTechEx addresses this challenge in a dedicated session titled ‘Printed Logic’ in its Printed Electronics Asia event, which will be conducted in Tokyo from October 2 to 3, 2012. Although a variety of materials like organics and oxides are used in the fabrication of thin film transistors, polycrystalline and amorphous silicon remain the leading technologies.
Today’s fabrication techniques are subtractive, whereas printing techniques are additive fabrication methods. It allows the direct deposition of a layer within three steps, thus reducing bill of materials and processing costs. These advantages are the driving factors that spur the research on printed thin film transistors. Other key benefits of printed thin film transistors include their ability to cover vast areas and their printability on low-temperature flexible substrates like paper. These advantages pave way to new markets such as point-of-sale posters, smart packaging, ultra large sensor arrays, and much more.
There are a variety of printable semiconductor available, including nanowires, carbon nanotubes, liquid silicon, crushed silicon, CdSe, oxides, and organics. Unfortunately, none of these semiconductors deliver a one-size-fits-all solution and all have their own limitations, which include, low mobility, low stability, low spatial uniformity, dielectrics, and low temperature annealing. Besides these technical challenges, the key go-to-market strategy of printed thin film transistors in several application fields is the substitution of an existing layer or component in a product. This is an issue as the current technology is well-established.
Printed transistors’ two key high-volume target markets are RFID tags and Displays. According to IDTechEx, printed thin film transistors will have to identify niche markets, which are probably on low-end disposable products. The printed circuits may require a few number of transistors and may only do simple logic. This approach may require ready-to-go printed logic platforms that can be integrated into end products. Since transistors are complex devices, huge investment and research and development efforts are required to upgrade them. This is a problem to this business model. Thus, manufacturers may not be willing to make investments due to lack of established target markets.