1. Materials Development: High-Performance Organic Semiconductors
We are dedicated to designing and synthesizing novel organic semiconductor materials with superior performance. Our key achievements include;
p-Type Organic Semiconductors with Suppressed Intermolecular Vibrations:
A series of p-type materials featuring π-conjugated backbones designed to suppress intermolecular vibrations and enhance intermolecular orbital overlap, leading to high charge carrier mobility.
p-Type Organic Semiconductors with Unique Molecular Orbitals:
A class of p-type materials possessing unique molecular orbital morphologies that effectively mitigate the negative impacts of intermolecular vibrations on charge transport.
n-Type Organic Semiconductors with Specific Intermolecular Interactions:
A series of n-type materials incorporating specific, non-covalent interactions, such as hydrogen bonding, to precisely control molecular packing and improve electron transport.
Mixed-Orbital Organic Semiconductors:
A group of materials where multiple molecular orbitals (e.g., HOMO, HOMO-1) contribute to charge transport, opening new avenues for materials design.
2. Process Development: Advanced Crystallization Methods for Maximizing Performance
The ultimate performance of organic semiconductors is realized in highly crystalline thin films, ideally in grain-boundary-free single crystals. Furthermore, precise control of the charge transport interface is critical for device performance. To this end, we have developed innovative solution-based crystallization methods.
By leveraging the unique characteristics of organic compounds, we have established large-area solution-crystallization techniques to fabricate single-crystalline thin films on a scale comparable to silicon wafers (e.g., 10 cm square class). Our focus is on producing ultrathin films, which are ideal for maximizing both material efficiency and device performance. We also develop molecular design strategies specifically tailored for these advanced processes.
For low-crystallinity polymer semiconductors, we have developed a film fabrication method that utilizes an ionic liquid surface to compress and align polymer chains, thereby enhancing their structural order.
We have also developed a potent and highly air-stable dicationic p-dopant. By applying this dopant to highly crystalline polymer semiconductors, we have successfully achieved both high crystallinity and a high doping state simultaneously, leading to the creation of highly conductive polymers.
This comprehensive suite of solution-processing techniques and advanced materials constitutes the key technologies and materials indispensable for next-generation electronics, including organic transistors (OTFTs), organic photovoltaics (OPVs), organic thermoelectric devices, and wireless power transfer systems.
代表的な研究成果
材料開発：高性能有機半導体材料の開発
・伝導を担うπ電子系骨格に分子間振動の抑制と分子間の軌道の重なりの増大を指向したp型有機半導体群
・分子間振動の影響低減を指向した特異な分子軌道形態を有するp型有機半導体群
・水素結合などの積極的な分子間相互作用を導入したn型有機半導体群
・複数の分子軌道が伝導に関わるミックスオービタル型有機半導体群
プロセス開発：有機半導体材料の最高性能を引き出すための塗布結晶化法および大面積結晶化法の開発
有機半導体の性能は得られる薄膜の結晶性に影響されており，「結晶粒界のない単結晶」において理想的な性能を発現します．また，伝導を担う界面の状態を「どのように制御するか」もデバイス性能に影響します．当研究室では，有機化合物の特長をいかし，また，シリコンウエハーに匹敵する10 cm角級の単結晶薄膜化（材料の使用効率およびデバイス性能を鑑みると超極薄膜が理想）を指向して，大面積塗布結晶化法および当該プロセスに適した分子設計法の開発に取り組んできました．また，結晶性が低い高分子半導体材料についても，イオン液体上で高分子鎖を圧縮配向させる薄膜化法の開発にも取り組んでいます．さらに，強力かつ高い大気安定性を有するジカチオン型pドーパントを開発し, 高結晶性高分子半導体に対してドーピングを施すことで，高結晶性と高ドープ状態の両立を達成し，高導電性高分子の開発にも成功しました．一連の塗布技術と材料群は，有機トランジスタ，有機薄膜太陽電池，有機熱電変換素子，さらにはワイヤレス給電素子などの次世代エレクトロニクスに欠かすことができないキーテクノロジーとキーマテリアルです．