対称性の異なる半導体分子による超分子層配列の自己形成を発見 ～溶媒不要な有機半導体の高均質塗布製膜が可能に～

2025-04-07 東京大学

＜関連情報＞

• https://www.t.u-tokyo.ac.jp/press/pr2025-04-07-001
• https://www.t.u-tokyo.ac.jp/hubfs/press-release/2025/0407/001/text.pdf
• https://www.science.org/doi/10.1126/sciadv.adv1878

対称・非対称有機半導体を用いた溶融混晶超薄膜共晶の形成 Melt-mixed superlayer cocrystal formation using symmetric and unsymmetric organic semiconductors

Kiyoshi Nikaido, Seita Kuroda, Satoru Inoue, and Tatsuo Hasegawa
Science Advances  Published:4 Apr 2025
DOI:https://doi.org/10.1126/sciadv.adv1878

Abstract

Organic molecules with a rigid, π-conjugated core (π-core) and flexible alkyl chains (C_n) naturally exhibit liquid crystal (LC) phases, promoting self-assembly of quasi–two-dimensional semiconducting layered crystals. However, particular roles of rigid and flexible parts in layer formations remain elusive. Here, we demonstrate formation of an unprecedented superlayer cocrystal phase via a unique smectic LC phase in the equimolar melt mixture of symmetrically distinct molecules. The molecules used are a monoalkylated [(π-core)-C_n] using 2-octyl[1]benzothieno[3,2-b][1]benzothiophene (mono-C₈-BTBT) and a dialkylated [C_n-(π-core)-C_n] using 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (di-C₈-BTBT). Thermal analyses show that the superlayer cocrystal is exclusively induced at the equimolar mixture via melt crystallization from the LC phase. X-ray structure analysis reveals a reversible C_n-(π-core)-C_n···(π-core)-C_n stacking arrangement in the superlayer cocrystal, where π-cores and alkyl chains form nearly independent layers. Notably, this melt crystallization allows solvent-free fabrication of semiconductive polycrystalline films for excellent thin-film transistors. These findings pave the way for tailoring a quasi–two-dimensional structure in LC materials toward molecular electronics.