Presentation Information
[10a-P03-1]Molecular Dynamics Simulations of Binary Organic Semiconductor Thin Films with Long and Short Alkyl Chains
〇Rikuo Suzuki1, Ryo Miyata2, Satoru Inoue3, Tatsuo Hasegawa2, Hiroyuki Matsui1 (1.ROEL, Yamaga Univ., 2.Dept. Eng., Univ. Tokyo, 3.INOEL, Yamagata Univ.)
Keywords:
Long-short chain mixed film,Organic transistor,Molecular dynamics simulation
This study used molecular dynamics (MD) simulations to investigate the microscopic behavior of alkyl chains in mixed films of Ph-BTBT-C6 and C12, asymmetric liquid crystalline organic semiconductors. These materials form unique monolayer-bilayer thin films and show increased friction, likely influenced by surface alkyl chain motion. Our all-atom MD models, based on X-ray diffraction, explored varying long-chain molar fractions (χ). Isolated C12 molecules exhibited increased gauche conformations towards their ends. However, as C12 concentration rose, steric hindrance from neighboring chains promoted trans-dominated conformations, leading to enhanced molecular ordering. A statistical model confirmed that the local number of adjacent long chains determined the trans ratio, reproducing experimental friction coefficients. Crucially, the gauche-trans transition frequency, indicating alkyl chain mobility, significantly decreased between χ = 0.3 and χ = 0.5. This suggests that conformational ordering reduces alkyl chain mobility. Areas of high friction correlated with suppressed bilayer stacking, attributed to interlayer frustration from surface disorder. In conclusion, alkyl chain disorder at the surface drives both energy dissipation and stacking inhibition, explaining the observed frictional behavior and unique film formation in these promising organic semiconductors.