Multiscale Modeling of the Electrostatic Impact of Self-Assembled Monolayers used as Gate Dielectric Treatment in Organic Thin-Film Transistors

Abstract

This study sheds light on the microscopic mechanisms by which self-assembled monolayers (SAMs) determine the onset voltage in organic thin-film transistors (OTFTs). Experiments and modeling are combined to investigate the self-assembly and electrostatic interaction processes in prototypical OTFT structures (SiO2/SAM/pentacene), where alkylated and fluoroalkylated silane SAMs are compared. The results highlight the coverage-dependent impact of the SAM on the density of semiconductor states and enable the rationalization and the control of the OTFT characteristics.

High-resolution spatial control of the threshold voltage of organic transistors by microcontact printing of alkyl and fluoroalkylphosphonic acid self-assembled monolayers

“…The fact that the mobility of the TFTs with the fluoroalkyl SAM is somewhat smaller than the mobility of the TFTs with the alkyl SAM is consistent with similar observations reported in the literature for various organic semiconductors [11][12][13][14]19,27]. One explanation that has been put forward by Mityashin et al based on results from a multiscale modeling study is related to the observation that the energetic disorder in the organic semiconductor layer is notably larger when the semiconductor is deposited onto a fluoroalkyl SAM, as opposed to an alkyl SAM [33], and that this larger energetic disorder leads to a smaller carrier mobility [34].…”

Structural Characterization of Alkylsilane and Fluoroalkylsilane Self-Assembled Monolayers on SiO2 by Molecular Dynamics Simulations

“…OTS achieves a higher orientational order than FDTS: this is a consequence of the difference in the torsional potential along the alkyl chain. 20 While the full trans conformer for − CH 2 −CH 2 − corresponds to an equilibrium angle of 180 degrees, and hence to perfectly linear chains with all the C-C bonds lying in a plane, for − CF 2 −CF 2 − the minimum is at about 160 degrees, and consequently the shape of the chain is more irregular and the order parameter is lower. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 we observe the typical alternation of the bond orientation for "odd" and "even" bonds, with increasing disorder moving towards the free surface.…”

“…42 To fill this gap, we present in the following detailed structural models of self-assembled monolayers arising from substituted alkyl-silanes grafted on amorphous silicon oxide surfaces, extending our previous study on the electrostatic effects of these SAMs on transistor characteristics. 20 NVT conditions, until energy equilibrium was reached.…”

Influence of the Surface Treatment on the Solution Coating of Single‐Crystalline Organic Thin‐Films

“…[30] Hence, surface treatment with intermediate surface energy offer the best compromise between wettability and electrical performance. In contrast to evaporation, high surface energy treatments are typically used for meniscus guided coating techniques as they provide good wetting for most commonly used organic solvents.…”