Composite materials improve the transmission rate of plastic electronic components

10/29/2022 10:46:15 AM

The response speed of smart phone to touch is determined by the flow rate of charge between various display components. Scientists from Imperial College London, London (ICL) and colleagues from King Abdullah University of Science and Technology (KAUST) will cooperate to manufacture organic thin film transistors (OTFT). These organic thin film transistors have continuously achieved record carrier mobility through a detailed solution treatment method that combines two organic semiconductors. These organic thin film transistors and their processing methods provide a series of future electronic applications.

Professor Aram Amassian's research team at King Abdullah University of Science and Technology cooperated with Dr. Thomas Anthopoulos from the Department of Physics in Imperial College London, London, Professor Iain McCulloch and Dr. Martin Heeney from the Department of Chemistry to develop and describe a composite material that can improve the charge flow rate and support the faster fabrication of organic transistors. They described this novel semiconductor mixture in a joint paper published in Advanced Materials.

In order to meet the challenge of expensive vacuum deposition process, organic synthetic chemists are becoming more and more effective in the synthesis of conjugated soluble small molecules. Dr. Anthopoulos, the chief researcher of Imperial College London, commented: "Although they tend to form large crystals, it is still a problem to repeatedly form high-quality, continuous and uniform films." In contrast, polymer semiconductors are often soluble and can form high-quality continuous films, but until recently, the charge carrier mobility of polymer semiconductors could not be higher than 1 cm 2/vs.

In this collective work, chemists in Imperial College London cooperated with the equipment physicists of the University's Plastic Electronics Center and the materials scientists of King Abdullah University of Science and Technology to integrate the advantages of polymers and small molecules into a composite material. The performance of this composite material is higher than that of each component taken out separately, and it also strengthens the reproducibility and stability from device to device.

The properties of the composites can be improved partly because of the crystal structure of small molecular components in the mixture and the flatness and smoothness of the top surface of polycrystalline films. The latter is very important for devices with upper gate and lower contact configuration, because the top surface of the semiconductor mixture forms a semiconductor dielectric interface when coated with polymer dielectric solution.

For highly polycrystalline small molecules in pure state, smooth and continuous surface and lack of surface grain boundaries are not common, which indicates that polymer adhesive can smooth semiconductor crystals, and may even coat semiconductor crystals with nano-scale thin layers. Professor Amassian, the co-author of the research paper, pointed out: "The performance of the mixture of polymer and molecule exceeds 5 cm 2 /Vs, which is very close to the single crystal mobility of the molecule itself published before."

Materials scientists at King Abdullah University of Science and Technology have solved the problems of phase separation, crystallinity and morphology analysis of organic semiconductor mixtures by combining Cornell high-energy synchrotron radiation source (CHESS) D1 beam line synchrotron radiation X-ray scattering technology, cross-section energy filtering transmission electron microscopy (EF-TEM) and topographic phase mode atomic force microscopy.

Professor Alberto Salleo of Stanford University is an expert in the characterization of advanced structures of polymer semiconductors. He said, "This work is particularly exciting because it shows that you can learn a lot about how they work by applying complementary and powerful characterization techniques to these complex organic mixtures. This is a research example of the relationship between structure and attribute, which highlights the effectiveness of this kind of cooperation. The mobility of 5 cm 2 /Vs is already an amazing number. The method described provides an opportunity for researchers to achieve higher mobility. "

Dr Anthopoulos added: "In principle, this simple mixing method can promote the development of organic transistors, making the functional characteristics of organic transistors far beyond the current highest level."

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