Organic Electronics Laboratory
Staff & Contact
| Educational Staff | Prof.Masakazu Nakamura Adjunct Prof.Masahiro Hiramotobr Associate Prof. Hiroaki Benten Adjunct Assistant Prof.Manish PANDEY |
|---|---|
| URL | https://mswebs.naist.jp/LABs/greendevice/index.html |
Education and Research Activities in the Laboratory
Let’s imagine electronic equipment that is easy to carry in a rolled state, a piece of fabric that generates electricity from the human body or a paper-like solar cell that generates electricity from light. Adding such unprecedented electronic functions onto various “surfaces”, human life will become more comfortable and prosperous. We are pursuing the realization of such novel electronic devices through studies elucidating unique phenomena in organic solids and applying the findings to the device functions using knowledge of solid-state physics, electronics, surface science, polymer physics, and molecular science. Our laboratory utilizes unique approaches made possible by our original characterization tools and computer simulations. We determine individual research projects ranging from basic science to development of operable devices, depending on the interests and aptitudes of the students. We foster independent thinking and a top-level mindset necessary for a researcher through collaborative research with institutes in Japan and overseas. Thus, we aim to cultivate researchers with a broad knowledge of science and a keen interest toward industrial applications.Research Themes
Four major ongoing research projects are presented here, but other collaborations are underway on a spot basis, especially on basic science topics.1. Control of Charge and Heat Transports by Molecular Junctions for Wearable Thermoelectric Generators
We are attempting to create novel thermoelectric materials and innovative flexible thermoelectric generators to convert exhaust heat from the living environment and the human body into electricity. We have found that the thermal conductivity of a carbon nanotube (CNT) composite decreases to 1/1000 by forming molecular junctions between nanotubes with a specially designed protein. The unique structural and mechanical character of CNT allow us to fabricate its composite yarn. With such a novel flexible thermoelectric material, we are aiming at the fabrication of “thermoelectric cloths” which can be handles like a normal cloths but generate electricity from body heat.
2. Basic and Applied Research on “Giant Seebeck Effect”
We are also trying to elucidate and control the Giant Seebeck Effect in organic semiconductors discovered in our laboratory with the aid of advanced measurement techniques, theoretical physics, and computational chemistry. The conventional theory of Seebeck effect takes only the charge transport within the band theory. However, in organic semiconductors, charge and molecular vibration are strongly coupled and, thereby, there sometimes appears up to 100-times larger Seebeck coefficient. Not only the scientific studies, we are also developing a way to utilize this new phenomenon to produce innovative thermoelectric generators.
3. Development of Next-Generation Plastic Solar Cells
We develop next-generation “plastic” solar cells based on p-type/n-type semiconducting polymers. To improve the solar cell performance, we elucidate photovoltaic conversion properties that are governed by nanoscale phase separation of polymers with a photoconductive atomic force microscopy. We also characterize the transport/recombination dynamics of photogenerated charge carriers in the device with an electrical impedance spectroscopy. Through understanding the nano structure-local electrical property-device function relationship, we have designed new device structures that can maximize the photovoltaic performance.
4. Development of Super Flexible ICs by Polymer Transistors
Carrier mobility in polymer semiconductors is high in the direction of the conjugated main chain. Therefore, the main chain of a polymer should be oriented parallel to the current flow. We are developing a new fabrication technique for highly oriented polymer semiconductors called the unidirectional floating film transfer method (UFTM). Floating films prepared on a liquid substrate by this method can be transferred onto various substrates. We aim to realize high-performance super-flexible electronic circuits using UFTM, by which novel electronic functions can be added onto various “surfaces”.
Recent Research Papers and Achievements
- M. Ito, et al., “From materials to device design of a thermoelectric fabric for wearable energy harvesters”, J. Mater. Chem. A 5, 12068 (2017).
- H. Kojima et al., “Universality of giant Seebeck effect in organic small molecules”, Mater. Chem. Front. 2, 1276 (2018).
- H. Benten et al., “Chain Aggregation Dictates Bimolecular Charge Recombination and Fill Factor of All-Polymer Blend Solar Cells” J. Mater. Chem. A 10, 21727 (2022).
- H. Benten et al., “Nanoscale Observation of the Influence of Solvent Additives on All-Polymer Blend Solar Cells by Photoconductive Atomic Force Microscopy” ACS Appl. Polym. Mater., 4, 169 (2022).
- M. Pandey et al., “Recent Advances in Orientation of Conjugated Polymers for Organic Field-Effect Transistors” J. Mater. Chem. C 7, 13323 (2019).
- M. Pandey et al., “Unidirectionally aligned donor-acceptor semiconducting polymers in floating films for high-performance unipolar n-channel organic transistors”, Adv. Electron. Mater., 9, 2201043 (2023).
- M. Suda et al., “Light-driven molecular switch for reconfigurable spin filters”, Nat. Commun. 10, 2455 (2019).