113th CEMS Colloquium


Prof. Jun Takeya (The University of Tokyo)


17:30 - 18:30, June 28, 2023 (Wednesday)


Okochi-Hall, RIKEN


Organic wisdom: low dimensional semiconductors and devices for smart sensing networks


    One of the expected missions of organic semiconductors has been to form ultra-low-cost platforms for analogue and digital circuits and to supply abundant devices for smart societies with IoT sensing networks. For this purpose, each sensing device requires not only primitive components such as thermistor but various circuits like amplifiers, AD converters, signal processors, and circuits for wireless communication, so that the prices are currently too high to prevail, say trillions of such smart sensing devices. The present seminar focuses on the material basis on the organic ultra-low-cost film-shaped devices and on the present status to gradually spread them to the market in a commercially driven scheme. 

 The presentation starts from fundamental material design strategy, the mechanism to achieve coherent high-mobility charge transport, and practical fabrication processes of the integrated circuits. The use of solution-crystalized organic single crystals opened the way to high-performance and low-cost production of integrated circuits (ICs) with more than 1,000 transistors, which is comparable to the level of typical ICs in 1980s. With the mobility exceeding 10 cm2/Vs, the operation speed is reaching 50 MHz, which is also comparable to the speed of silicon circuits in 1980s. The single-crystal wafers are ultimately two-dimensional with 30cm x 30cm in size and only less than 10 nm thick, so that material consumption is negligibly small resulting in very low cost for the semiconductor material. In addition, microwave power is supplied to the circuits with sufficient power because of recently developed ultra-fast diode circuits.

 Low temperature electronic states of the coherent charge transport, which is indeed responsible for the low-cost high-performance circuits in the non-covalent bonded organic molecules, is recently studied to offer platforms of organic quantum electronics. Metallic phase is already achieved down to a few K in heavily doped organic semiconductor crystals. The low-temperature metallic phase appears somewhat exotic with strong electronic correlation.

 The concluding part of the presentation is devoted to several ongoing application of the above material sciences to practical usage. Temperature, vibration and location sensors with organic circuits are already commercialized for small-scale practical use. Furthermore, since impact of numbers of sensors exponentially increases in proportion to possible combination of the data, connection of multiple sensors enables large-scale machine leaning to provide various advantages, ranging from reliable analysis with low noise and error-free data processing to broad-range services of connecting humans and society. Some examples are already starting to be introduced, so that the society of “organic wisdom” is approaching.