title: Thiophene-Diketopyrrolopyrrole-Based Quinoidal Small Molecules as Solution-Processable and Air-Stable Organic Semiconductors: Tuning of the Length and Branching Position of the Alkyl Side Chain toward a High-Performance n-Channel Organic Field-Effect Transistor.
abstract: A series of thiophene-diketopyrrolopyrrole-based quinoidal small molecules (TDPPQ-2-TDPPQ-5) bearing branched alkyl chains with different side-chain lengths and varied branching positions are synthesized. Field-effect transistor (FET) measurement combined with thin-film characterization is utilized to systematically probe the influence of the side-chain length and branching position on the film microstructure, molecular packing, and, hence, charge-transport property. All of these TDPPQ derivatives show air-stable n-channel transporting behavior in spin-coated FET devices, which exhibit no significant decrease in mobility even after being stored in air for 2 months. Most notably, TDPPQ-3 exhibits an outstanding n-channel semiconducting property with electron mobilities up to 0.72 cm(2) V(-1) s(-1), which is an unprecedented value for spin-coated DPP-based n-type semiconducting small molecules. A balance of high crystallinity, satisfactory thickness uniformity and continuity, and strong intermolecular interaction accounts for the superior charge-transport characteristics of TDPPQ-3 films. Our study demonstrates that tuning the length and branching position of alkyl side chains of semiconducting molecules is a powerful strategy for achieving high FET performance.
authors.affiliation: †Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.|‡University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.affiliation: †Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.|‡University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yunke
authors.initials: Y
authors.lastname: Qin
authors.affiliation: †Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.|‡University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yuanhui
authors.initials: Y
authors.lastname: Sun
authors.affiliation: †Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.|‡University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Ying-Shi
authors.initials: YS
authors.lastname: Guan
authors.affiliation: †Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: †Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Daoben
authors.initials: D
authors.lastname: Zhu
keywords: alkyl-side-chain engineering; diketopyrrolopyrrole; n-type organic semiconductors; quinoidal molecules; spin-coated OFETs