[17p-W2_402-1~14] 12.1 Fabrications and Structure Controls

2:45 PM - 3:00 PM JST(5:45 AM - 6:00 AM UTC)Presentation by Applicant for JSAP Young Scientists Presentation Award

[17p-W2_402-6] Structural Determination of Thin-Film Phases Unique to Liquid-Crystalline Organic Semiconductors

〇Takayuki Oka¹, Nobutaka Shioya¹, Takeshi Hasegawa¹ (1.ICR, Kyoto Univ.)

Keywords:

Spin-coating,2D-GIXD,Infrared specroscopy

Organic semiconductors offer a unique advantage in thin-film fabrication through solution processing. Ph-BTBT-C₁₀, a high-performance organic semiconductor, achieves excellent surface uniformity when spin-coated onto heated substrates, where film formation proceeds via a supercooled smectic E (SmE) liquid-crystalline phase. However, the molecular origin of this uniformity has remained unclear. In this study, we fabricated spin-coated Ph-BTBT-C₁₀ films and investigated their structure using two-dimensional grazing-incidence X-ray diffraction (2D-GIXD) and infrared spectroscopy. The diffraction patterns revealed rod-like features characteristic of two-dimensional crystals, distinct from previously reported vacuum-deposited films. Structural modeling combined with computational analysis showed that the resulting crystal structure retains key features of the SmE phase. Infrared spectral analysis further indicated that the alkyl side chains adopt relatively disordered conformations, partially preserving the molten-like state of the SmE phase. These disordered side chains are considered to suppress three-dimensional aggregation, thereby promoting two-dimensional crystal growth and enhancing macroscopic surface uniformity of the film.