SustainablE quantuM nANomaTerials & devICeS
(SEMANTICS) - BISRI研究室
Our Research
In SEMANTICS, we create various solutions-processable nanomaterials, particularly colloidal quantum dots, and develop different optoelectronic, energy harvesting and energy storage devices. We are curious to study the quantum confinement effect in different kinds of compounds when we make them into nanometer objects. They will show unique properties different from their bulk materials so that we can utilize them in new applications. From a different perspective, creating such nanoscale objects with different properties also means making artificial giant atoms. We can assemble these giant atoms to form superlattices and become new solid-state materials from which novel properties can emerge.
SEMANTICS performs interdisciplinary research that spans from the chemistry of material synthesis, intensive investigation of the physical properties, and the engineering of new optoelectronic and energy harvesting devices. At the heart of our research, we are exploring possibilities to find more sustainable ways to create and utilize the finite resources of materials. Also, we want to find solutions for creating a low carbon footprint society by providing alternative ways to harvest and store energy and reduce its consumption by exploiting quantum nanomaterial properties.
01
Development of novel sustainable nanoparticles and quantum dots
Colloidal quantum dots as giant atoms is one of the keywords of our research. Through colloidal synthesis, we can mix two or more chemical precursors to let them react and grow to become nanocrystals. By optimizing various parameters surrounding the colloidal synthesis, we can control the size and shape of the nanocrystals so that they will exhibit quantum confinement phenomena and behave as quantum dots. These inorganic nanocrystals will be protected by organic molecular ligands that provide them solubility in various solvents. Furthermore, colloidal synthesis can sometimes create nanocrystal compounds whose crystal structures are challenging to find in their natural and bulk material forms. It will allow us to discover new materials with new properties. Currently, our primary interest is establishing various new nanocrystals from abundant sources with minimal carbon footprints.
02
Electrical transport in colloidal quantum dot assemblies and the other solution-processable nanomaterials
For many optoelectronic, energy harvesting and energy storage devices, electronic transport is one of the most critical parameters. So far, it is still the main bottleneck for using colloidal quantum dot assemblies in those practical applications. Until now, many of the theoretical prospects of this class of materials (for solar cells, thermoelectric, etc.) have not been ultimately materialized due to the mediocre charge transport from one quantum dot to another. Therefore, using various tools, our group intensively investigates the relationship between the structure of the quantum dot assemblies and the related charge transport properties. Building field-effect transistors of these quantum dots is among the essential tools to investigate their charge carrier transport properties. For this purpose, we also develop a technique that utilizes the so-called electric double-layer transistor, in which electrolytes control the number of charges that flow within the assembly of the quantum dots. These techniques are also helpful in exploring potential applications of the materials for different kinds of devices based on transistors, including sensors.
03
Novel energy storage devices
Our group is focused on enhancing supercapacitors through structured CQD assemblies, aiming to overcome limitations in energy density and power delivery typical in traditional supercapacitors. We explore the development of high-performance supercapacitors using colloidal quantum dot (CQD) assemblies to boost energy storage and charge mobility. By structuring CQDs in densely packed, hierarchical porous formations, we create surfaces that enhance ion accessibility and storage, balancing conductivity with efficient ion diffusion. Techniques like layer-by-layer dip-coating allow precise control over assembly structure, enabling us to maximize energy storage density without compromising ion accessibility or conductivity. Additionally, we leverage defect-engineering in nanomaterials that elevate quantum capacitance. This combination of CQD architectures and engineered materials allows us to create scalable, high-efficiency energy storage devices that align with growing demands for sustainable, fast-charging power sources.
04
Energy harvesting devices
Our research focuses on utilizing colloidal quantum dots (QDs) in designing advanced solar cells, photodetectors, and thermoelectric devices. The quantum confinement effect in QDs enables fine control over band gaps and electronic properties, allowing us to tailor materials for efficient light absorption and charge transport. We explore a variety of device architectures to leverage the benefits of QD integration.By refining ligand chemistry and device assembly methods, we optimize electron mobility and mitigate issues related to surface traps, significantly improving the efficiency of QD-based solar cells and photodetectors.
In our search for next-generation thermoelectric materials, we are examining the potential of colloidal QDs for efficient thermal-to-electric conversion. QDs offer tunable energy levels that facilitate optimized energy filtering, a mechanism crucial for high thermoelectric efficiency. By systematically controlling QD size, composition, and surface chemistry, we are exploring pathways to enhance the thermoelectric properties of nanomaterials, aiming to develop materials with low thermal conductivity and high electrical performance. Our multidisciplinary approach to device physics and engineering in energy-harvesting applications positions us to address both the efficiency and environmental sustainability challenges of future energy technologies
05
Iontronics: Ion-Controlled Electronics
Our research in iontronics—a multidisciplinary field focused on controlling electronic properties via ion motion and spatial arrangement—explores a wide variety of colloidal quantum dots (CQDs) and other advanced nanomaterials, including carbon nanotubes, to advance electron transport, energy storage, and nanoelectronic technologies. This work enables unique material assemblies that offer tunable functionalities and versatile applications. We engineer CQD and nanomaterial structures to form superlattices and hierarchical porous architectures, which are specifically designed to optimize ion interactions, enhance charge mobility, and enable adaptability across various electronic devices. Leveraging electric-double-layer transistors (EDLTs), a core tool in iontronics, we achieve precise control over charge carriers and induce transformative phase transitions, such as insulator-to-metal transitions, within CQD assemblies. This high level of modulation unlocks new functionalities, including high-capacitance states similar to supercapacitors, establishing CQDs and related nanomaterials as essential components in next-generation nanoelectronics.
Looking ahead, these iontronic devices based on CQDs and the other developed nanomaterials hold significant promise for applications in sensors, neuromorphic computing, edible electronics, and nanoelectronics.