Molecular dynamics simulations of graphoepitaxy of organic semiconductors, sexithiophene, and pentacene: Molecular-scale mechanisms of organic graphoepitaxy

Abstract

Molecular dynamics (MD) simulations of the organic semiconductors α-sexithiophene (6T) and pentacene were carried out to clarify the mechanism of organic graphoepitaxy at the molecular level. First, the models of the grooved substrates were made and the surfaces of the inside of the grooves were modified with -OH or -OSi(CH 3 ) 3 , making the surfaces hydrophilic or hydrophobic. By the MD simulations of 6T, it was found that three stable azimuthal directions exist (0, >45, and 90°; the angle that the c-axis makes with the groove), being consistent with experimental results. MD simulations of deposition processes of 6T and pentacene were also carried out, and pentacene molecules showed the spontaneous formation of herringbone packing during deposition. Some pentacene molecules stood on the surface and formed a cluster whose a-axis was parallel to the groove. It is expected that a deep understanding of the molecular-scale mechanisms will lead graphoepitaxy to practical applications, improving the performance of organic devices.

Early Stage Growth Process of Dinaphtho[2,3‐b:2',3'‐f]thieno[3,2‐b]thiophene (DNTT) Thin Film

“…For example, an amorphous SiO 2 surface was prepared and used for MD simulations without hydrogen termination or self‐assembled monolayer (SAM) treatment, which has been performed in many studies. [ 23–27 ] Undeniably, there may be strong interactions between the surface and molecules that were not originally anticipated. However, these results capture the trends in DNTT growth on SiO 2 surfaces.…”

Water permeation pathways in laminated organic single-crystal devices

“…The full details of the MD simulations are explained elsewhere, 31,32 however, briefly, the water-water interaction was calculated based on the TIP5P potential, 33 and the intermolecular and molecule-substrate interactions were described by the Lennard-Jones potential, as well as Coulomb interactions that were summed up within the cut-off distance of 1 nm. Under these simulation conditions water molecules have been confirmed to form a massive aggregate on a hydrophobic surface and to spread over a hydrophilic surface, 31 which validates the employed conditions for the MD simulations. the centroid of the water molecules moved toward the rubrene surface and the water molecules spread to some extent over the surface.…”

Molecular dynamics simulations of pentacene thin film growth: Stability of nuclei comprising standing molecules and their subsequent growth

“…In this study, the author focuses on the stability of the clusters which comprise the standing molecules (the molecules which have already stood up) and investigates the stability of such clusters by MD simulations. Some years ago, 17) the author started MD simulations to investigate the mechanism of graphoepitaxy [18][19][20] of organic semiconductor molecules and published the results of the MD simulations. 17) In this study, the technique of MD simulations established in Ref.…”

“…Some years ago, 17) the author started MD simulations to investigate the mechanism of graphoepitaxy [18][19][20] of organic semiconductor molecules and published the results of the MD simulations. 17) In this study, the technique of MD simulations established in Ref. 17 was utilized.…”

“…Please refer to Ref. 17 for more details about the mathematical expressions of interaction potentials (force field).…”