Single-layer organic transistors with electrodes attached to the field-effect transistor (Field-effect transistor, FET) are electronic components used to control current in electronic products, used in integrated circuits, computer central processing units, display drive components, etc. Few core components of modern electronic products. Organic field-effect transistors (OFET) use organic materials as semiconductor current channels. Compared with inorganic semiconductors that use materials such as silicon (Silicon), OFET has the characteristic advantage of flexibility.
OFET has the advantages of high sensitivity, mechanical flexibility, biocompatibility, and adjustability of material properties. The manufacturing cost is also low, which greatly enhances its potential to be applied to new products, such as wearable electronic devices, and health designed to match the human body line. Monitor, and rollable screen, etc. Imagine this: In the future, TV screens can be rolled up for collection and unfolded to play images; wearable smart electronic products are used more widely and diversified; clothing can be worn on the body to collect various vital signs data in real time, and give instant feedback. Notify users and medical personnel of unusual circumstances. In precision medical applications, micro-robots made of harmless organic materials can work in the human body to assist in diagnosing diseases, delivering targeted drugs, performing minimally invasive surgery, and other medical purposes.
However, so far, it has been very difficult to reduce the size of OFETs, which has become a major obstacle to improving the performance of related electronic products, limiting its prospects for wider commercial applications. At present, some electronic devices using OFETs on the market are not ideal in terms of flexibility or durability, and are still in the early stages of technology.
The engineering team led by Dr. Chen Guoliang, associate professor of the Department of Mechanical Engineering of the University of Hong Kong, has recently successfully developed a new monolayer organic semiconductor transistor (staggered structure monolayer OFETs), laying a new cornerstone for the future technological development of reducing the size of OFETs.
Under the microscope, peel off the metal electrode from the original substrate and transfer it to the transistor
The team adopted an electrode transfer method that uses the high surface characteristics of an ultra-flat single-layer surface to "stick" metal electrodes without using any interface layer. The method is similar to the important scientific research achievement of cartoon stickers for children. It has been published in the academic journal "Advanced Materials", and the team has applied for a US patent for the results.
The main problem facing scientists at present is that once the unit area of OFET is reduced, its performance will drop accordingly. Part of the reason is the problem of contact resistance, which is the resistance to current flow between contact surfaces. When the volume of the OFET becomes smaller, the contact resistance becomes the leading factor that reduces its performance and affects the performance of electrical products.
The interlaced single-layer OFET successfully developed by Dr. Chen’s team can achieve a record low contact resistance of 40 Ω-cm. Compared with the current conventional OFET with a contact resistance of 1000 Ω-cm, it is new at the same current level. OFET can reduce the power dissipation of the contact surface by 96%. More importantly, in addition to saving energy, the new OFET greatly reduces the waste heat generated by the system, and can solve the current key and old problem of overheating the system that hinders the development of semiconductors by reducing the size of semiconductors to improve the performance of electronic devices without increasing their size.
Dr. Chen said: "Based on this research, we are expected to reduce the size of OFETs to sub-micron level in the future, shortening the distance from inorganic FETs, and at the same time give full play to the advantages of its organic characteristics. The key to globalization."
"If the highly flexible OFET succeeds in the end, many traditional rigid electronic devices, such as monitors, computers and mobile phones, will see revolutionary developments in the future. They can easily change shape, curl and fold, etc., with lighter weight and lower production costs. "
"In addition, the biocompatibility of OFET's organic characteristics is conducive to the research and development of advanced medical equipment, which are used in the human body to track brain or neuron activity, and for accurate diagnosis of brain-related diseases such as epilepsy. Frontier category." Dr. Chen added.
Dr. Chen’s team is currently working with researchers from the Hong Kong University School of Medicine and bioengineering scholars from the City University of Hong Kong to integrate the micro OFET into a flexible circuit, connect it to a polymer microprobe, and implant it in the brain of a mouse , To detect its neuronal activity under various external stimuli. They also plan to combine OFET with surgical tools (such as catheters), and then implant them into the animal's brain to directly sense its brain activity to find the exact location of the abnormal activity.
"The OFET we developed has a very good signal-to-noise ratio (signal-to-noise ratio) in the signal detection of neuron activity, and has the opportunity to capture some weak signals that were not detected by traditional electrodes in the past, bringing breakthrough development. "Dr. Chen explained.
Dr. Chen concluded: “Our ultimate goal is to combine applied research with basic science, and hope that the research results can broadly expand the scope of research and application of OFET. We believe that, according to the current development pace of OFET technology, it will be used in large display panels and surgical tools. It is ready for applications in other aspects."