Effect of Alkyl Chain Length on Charge Transport Property of Anthracene-Based Organic Semiconductors

Dongwei Zhang; So Yokomori; Ryohei Kameyama; Changbin Zhao; Akira Ueda; Lei Zhang; Reiji Kumai; Youichi Murakami; Hong Meng; Hatsumi Mori

doi:10.1021/acsami.0c16144

Effect of Alkyl Chain Length on Charge Transport Property of Anthracene-Based Organic Semiconductors

ACS Appl Mater Interfaces. 2021 Jan 13;13(1):989-998. doi: 10.1021/acsami.0c16144. Epub 2020 Dec 17.

Authors

Dongwei Zhang¹, So Yokomori¹, Ryohei Kameyama¹, Changbin Zhao², Akira Ueda^{1

3}, Lei Zhang¹, Reiji Kumai⁴, Youichi Murakami⁴, Hong Meng², Hatsumi Mori¹

Affiliations

¹ The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
² School of Advanced Materials, Peking University Shenzhen Graduate School, Peking University, Shenzhen 518055, China.
³ Department of Chemistry, Faculty of Advanced Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
⁴ Condensed Matter Research Center (CMRC) and Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 3050801, Japan.

PMID: 33332081
DOI: 10.1021/acsami.0c16144

Abstract

Anthracene, a simple planar building block for organic semiconductors, shows strong intermolecular interactions and exhibits strong blue fluorescence. Thus, its derivatives have a great potential to integrate considerable charge carrier mobility and strong emission within a molecule. Here, we systematically studied the influence of alkyl chain length on the crystal structures, thermal properties, photophysical characteristics, electrochemical behaviors, and mobilities for a series of 2,6-di(4-alkyl-phenyl)anthracenes (C_n-Ph-Ants, where n represents the alkyl chain length). Among them, C_n-Ph-Ants (n = 0, 1, 2, and 3) display similar layered herringbone (LHB) packing motifs, which facilitate two-dimensional charge transport and thereby enables high-performance organic field-effect transistors (OFETs). All C_n-Ph-Ants exhibit similar work functions and show strong blue fluorescence with photoluminescence quantum yields (PLQY) of approximately 40% in toluene. In addition, the absolute powder PLQYs of C₀-, C₂-, C₃-, C₄-, and C₆-Ph-Ants are 24.6, 8.2, 5.7, 10.9, and 8.6%, respectively. Note that the alkyl chain length shows a significant effect on the charge mobilities of C_n-Ph-Ants. Our newly synthesized C₁-, C₃-, and C₄-Ph-Ants show hole mobilities of up to 2.40, 1.34, and 1.00 cm² V^-1 s^-1, respectively, with mobilities of 3.40, 1.57, and 0.82 cm² V^-1 s^-1 for C₀-, C₂-, and C₆-Ph-Ants, indicating an increasing tendency of mobility with shorter alkyl chain length. This feature is related to the microstructures of the thin films, which reveal the enhanced film order, crystallinity, and grain size with a decrease in the alkyl chain length. Moreover, we theoretically analyze the intermolecular transfer integrals of HOMOs, which increase at T-shaped contacts as the alkyl chain length decreases, which improves the intermolecular charge transport properties, leading to the increases in mobility. Interestingly, the anisotropy of the transfer integral tends to decrease upon substitution with longer alkyl chains, suggesting that alkyl chain adjustments may facilitate isotropic charge transport property in 2,6-alkylated anthracenes.

Keywords: anthracene; organic semiconductor; organic thin-film transistor; p-type.