Solution processable dithioalkylated methylidenyl cyclopentadithiophene based quinoidal small molecules for n-type organic field-effect transistors

Shakil N. Afraj, Meng Hao Lin, Chih Yao Wu, Arulmozhi Velusamy, Ping Yu Huang, Tzu Yu Peng, Jui Chen Fu, Shih Hung Tung, Ming Chou Chen, Cheng Liang Liu

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

A new series of cyclopentadithiophene (CDT)-based quinoidal semiconductors—CDTSQ-8 (1), CDTSQ-10 (2), CDTSQ-12 (3), and CDTSQ-14 (4)—with various dithioalkylated-methylidenyl side chains were designed and synthesized as n-type organic small molecules for solution-processable organic field-effect transistors (OFETs). The physical, electrochemical, and electrical properties of these new compounds were thoroughly investigated. Further, single-crystal structures of CDTSQ-10, CDTSQ-12, and CDTSQ-14 were obtained. Optimized geometries obtained from single-crystal X-ray diffraction revealed the planarity of the central core. The smaller dihedral angle between dithioalkyl methylene and the CDT core (4.8°), a planar molecular structure, short main-core stacking distance (3.43 Å), short intramolecular (S⋯H), and intermolecular (S⋯N, N⋯H, and N⋯N) distances of the CDTSQ-12 molecule suggest good conditions for the extended π-orbital interaction of the corresponding molecule, resulting in better device performance. The favorable molecular packing and low-lying LUMO energy level (−4.10 eV) suggest that CDTSQs could be electron-transporting semiconductors. Thin-film morphological analysis by grazing-incidence wide-angle X-ray scattering revealed that all CDTSQ molecules are stacked on the substrate in an edge-on fashion. OFETs based on solution-sheared CDTSQ-12 exhibited the highest electron mobility of 0.14 cm2 V−1 s−1 with good ambient stability. The electron mobility of solution-processable CDTSQ is 14 times larger than that of a previously reported dilakylated-CDT-based CDTRQ (0.01 cm2 V−1 s−1, vacuum-processed) quinoidal derivative. These results demonstrate that side-chain engineering can improve the device performance of solution-sheared CDTSQ organic semiconductors.

Original languageEnglish
Pages (from-to)14496-14507
Number of pages12
JournalJournal of Materials Chemistry C
Volume10
Issue number39
DOIs
StatePublished - 16 Aug 2022

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