The University of Tokyo · Engineering
Professor Yu Yamashita's research lab focuses on the design, synthesis, and application of advanced organic semiconductors, particularly conjugated polymers and single crystals, for next-generation flexible and printed electronics. The lab specializes in controlling molecular and nano-scale ordering to achieve high charge carrier mobility and efficient electrical doping, with a strong emphasis on band-like transport and ion-exchange doping strategies. Key research directions include molecular doping mechanisms, structural control of polymer thin films, and the development of high-performance, air-stable organic field-effect transistors and strain sensors. The lab combines advanced characterization techniques with computational simulations to understand and optimize charge transport in complex soft materials.
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ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTMobility Exceeding 10 cm2/(V·s) in Donor–Acceptor Polymer Transistors with Band-like Charge TransportYu Yamashita†, Felix Hinkel‡, Tomasz Marszalek‡, Wojciech Zajaczkowski‡, Wojciech Pisula‡§, Martin Baumgarten‡, Hiroyuki Matsui*†, Klaus Müllen*‡, and Jun Takeya*†View Author Information† Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8561, Chiba, Japan‡ Max Planck Institute for Polymer Research,
Abstract Self-organization in π -conjugated polymers gives rise to a highly ordered lamellar structure, in which inter-chain stacking spontaneously forms two-dimensional conjugated sheets. This multi-layer stacked nature of semicrystalline polymers allows the inclusion of various functional molecules. In particular, redox-triggered ion-intercalation is an ideal system for molecular doping, for which extremely high charge carrier density has been achieved. Here, we conducted a detailed structural
Air stability of n-doped polymers is improved by using a strongly reducing, dimeric dopant instead of cobaltocene.
Abstract Control of electrical doping is indispensable in any semiconductor device, and both efficient hole and electron doping are required for many devices. In organic semiconductors, however, electron doping has been essentially more problematic compared to hole doping because in general organic semiconductors have low electron affinities and require dopants with low ionization potentials that are often air-sensitive. Here, we adapt an efficient molecular doping method, so-called ion-exchange
Organic semiconductor (OSC) single crystals feature flexibility, solution processability, and high-mobility coherent carrier transport, which are advantageous for printed flexible electronic applications. A mechanical strain sensor is a target device whose high sensitivity and wide measurement range have been demonstrated when OSC single crystals were employed as the active channel. However, there have been limited reports on scalable fabrication of devices and reliable measurements, which limit
3D wiring technology is required for the integration of micro-nano devices on various 3D surfaces. However, current wiring technologies cannot be adapted to a variety of materials and surfaces. Here, we propose a new metal deposition method using only a micro-plasma bubble injector and a metal ion solution. Micro-plasma bubbles were generated on demand using pulses, and the localized reaction field enables metal deposition independent of the substrate. Three different modes of micro-plasma bubbl
Orientational control of polymeric semiconductors (PSs) is a fundamental technology for understanding and improving the carrier transport properties. Although PS thin films have been fabricated through facile solution processes, complex convection flows during solvent evaporation often limit the scalability and reproducibility of orientational control. To address these problems, we developed a circular flow alignment method for PS thin films. PS solutions were dropped on glycerol flowing in a ci
A pyrometallurgical process of metal recycling from waste lithium-ion batteries (LIB) has been developed. Basic process is that Co, Ni oxides which are from cathode materials of LIB and Cu which is from anode current collector are smelted and are reduced to metal, and the metal is refined in a next hydrometallurgical process. Since Al and Li contained in LIB are distributed to slag as oxides in the melting process, it is important to know the influence of these elements on the melting temperatur
Using ion-exchange doping under ambient conditions, combinations of a polymeric semiconductor and dopant anions were studied to achieve high stability and work function.
Thin-film devices that transduce the chemical activity of ions into electronic signals are essential components in various applications, including healthcare diagnostics and environmental monitoring. Combinations of organic semiconductors (OSCs) and ion-selective materials have been explored for developing solution-processable ion sensors. However, the necessity of reference electrodes (REs) and operational stability in ion-permeable OSCs have posed questions regarding whether reliable measureme
This paper presents a laser direct writing method for the fabrication of a laser-induced graphitic carbon (LIGC)/polydimethylsiloxane (PDMS) bimorph thermal microactuator via two-photon polymerization (TPP) and laser-induced graphitization (LIG). The fundamental parameters of femtosecond laser dotting, adopted as the writing mode for LIG, were investigated by observing the carbonized surface of the TPP-written PDMS plate using optical, scanning electron, and Raman microscopies. Subsequently, as
We propose an innovative concept, "On-demand metal deposition by micro-plasma bubble" which enable us to fabricate microelectrode with no limit by the conductivity and shape of target. We confirm a micro-plasma bubble generation by local discharge which is a key mechanism of our proposed method. The micro-plasma bubble has strong reduction effect, and we achieved deposition of the copper at and arbitrary position on glass, silicon wafer and nitrile rubber by reducing the copper ions in the solut
Solution processing of organic semiconductors provides a facile way to fabricate electrically doped thin films, which opens opportunities for advancing printed electronics. However, this approach is limited due to the instability of dopants and doped organic semiconductors, particularly for n-type ones. In this study, n-type doping of an organic semiconducting polymer is achieved using aqueous doping solutions in air, a condition under which n-type chemical doping had not previously been demonst
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