Formation of high-performance thermoelectric materials by control of intermolecular chemical bonds between functional molecules

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K22049
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Nagoya University
• Principal Investigator: Nakaya Masato 名古屋大学, 工学研究科, 准教授 (30725156)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: エネルギーハーベスティング / 熱電変換 / ゼーベック効果 / 有機材料 / フラーレン / 重合反応 / 有機薄膜 / ウェアラブルデバイス

Outline of Final Research Achievements

High performance and flexible thermoelectric (TE) conversion devices are expected to be power sources for enormous number of wearable devices for future Internet-of-Things (IoT). Although a fullerene C60 film is one of candidates of novel flexible TE materials because of its giant Seebeck coefficient (S > 100 mv/K) at around room temperature, improvement of its very low electrical conductivity (σ: ~10-5 Ω-1cm-1) is required for practical use. However, it is generally difficult to realize TE materials exhibiting large values of both S and σ simultaneously owing to the trade-off relationship between them in bulk materials.
In this research project, I demonstrated that the σ is improved with maintaining a giant S for the C60 film by formation of intermolecular covalent bonds between adjacent C60 molecules. This is the novel methodology for control of TE property of organic semiconductors.

Free Research Field

ナノサイエンス、ナノ計測、ナノ物質科学、ナノエレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

有機半導体の示す巨大ゼーベック係数S（S > 数10 mV/K）を保持しつつ、導電率σを向上させることができれば、柔らかく高性能な熱電素子への応用が拓かれる。分子薄膜のσを向上させる手法としては、不純物添加によるキャリアドープがより一般的であるものの、この方法では、σの増加と共にS値の著しい減少が起きる。本研究では、分子間結合の形成によって、分子薄膜の巨大Sを保持しながらσを向上させることに初めて成功した。この方法論を様々な有機半導体へ応用することでＳとσが共に優れた値を示す高性能熱電材料の創製へと道が拓かれる。