Solution‐Processable Dithienothiophenoquinoid (DTTQ) Structures for Ambient‐Stable n‐Channel Organic Field Effect Transistors

Abstract

A series of dialkylated dithienothiophenoquinoids (DTTQs), end‐functionalized with dicyanomethylene units and substituted with different alkyl chains, are synthesized and characterized. Facile one‐pot synthesis of the dialkylated DTT core is achieved, which enables the efficient realization of DTTQs as n‐type active semiconductors for solution‐processable organic field effect transistors (OFETs). The molecular structure of hexyl substituted DTTQ‐6 is determined via single‐crystal X‐ray diffraction, revealing DTTQ is a very planar core. The DTTQ cores form a “zig‐zag” linking layer and the layers stack in a “face‐to‐face” arrangement. The very planar core structure, short core stacking distance (3.30 Å), short intermolecular SN distance (2.84 Å), and very low lying lowest unoccupied molecular orbital energy level of −4.2 eV suggest that DTTQs should be excellent electron transport candidates. The physical and electrochemical properties as well as OFETs performance and thin film morphologies of these new DTTQs are systematically studied. Using a solution‐shearing method, DTTQ‐11 exhibits n‐channel transport with the highest mobility of up to 0.45 cm2 V−1 s−1 and a current ON/OFF ratio (ION/IOFF) greater than 105. As such, DTTQ‐11 has the highest electron mobility of any DTT‐based small molecule semiconductors yet discovered combined with excellent ambient stability. Within this family, carrier mobility magnitudes are correlated with the alkyl chain length of the side chain substituents of DTTQs.

Recent Progress in High‐Mobility Organic Transistors: A Reality Check

“…Synthetically less complex three ring systems have also been reported, such as dithienothiophenoquinoids ( SM3 ) and quinoidal benzo[1,2‐ b :4,5‐ b ]dithiophene ( SM4 ) . Both materials have LUMO levels below −4.2 eV and are reported to produce OTFTs with good ambient stability.…”

Solution‐Processed High‐Performance Tetrathienothiophene‐Based Small Molecular Blends for Ambipolar Charge Transport

“…For instance, small molecular organic semiconductors have shown excellent hole mobilities exceeding 43 cm 2 V −1 s −1 in solution processed OFETs, and exhibited power conversion efficiencies well over 10% in organic photovoltaics . Most of the organic molecular semiconductors studied to date usually consist of π‐conjugated cores bridged by donor units such as benzothiophenes ( BTs ), dithienosiloles ( DTS ), thienothiophenes ( TT ), dithienothiophenes ( DTT ), and tetrathienoacenes ( TTA ) . Among these building blocks, fused thiophenes (such as TT , DTT , and TTA ) are attractive π‐bridging units due to their strong intermolecular S∙∙∙S interactions, extensive intramolecular π‐conjugation, and close intermolecular π–π stacking.…”

“…In contrast, benzodifurandione, naphthalenediimides ( NDI ), perylenecarboxydiimide ( PDI ), diketopyrrolopyrroles ( DPP ), perfluorophenyl, and alkyl cyanoacetates are electron‐deficient π‐architectures and crucial units for constructing n‐type semiconductors . For example, fluorinated DFP‐DTT and DFP‐TTA as well as cyanated quinoids DTTQ and CMUT exhibited high n‐type carrier mobilities of 0.07–0.9 cm 2 V −1 s −1 (structures and mobilities are shown in Figure S1, Supporting Information) …”

“…DbT‐TTAR ( 2 ) affords the highest hole mobility of up to 0.36 cm 2 V −1 s −1 . Thus, next, ambipolar blends were investigated by utilization of this highest p‐type performance organic semiconductor of this family and the recently developed n‐type quinoidal structure DTTQ‐11 as the hole and the electron‐semiconductor components, respectively. The highest balanced ambipolar transport was achieved for a 1:1 weight ratio of DbT‐TTAR : DTTQ‐11 blend composition and exhibited hole and electron mobilities of 0.83 and 0.37 cm 2 V −1 s −1 , respectively.…”

A Ladder-Type Organosilicate Copolymer Gate Dielectric Materials for Organic Thin-Film Transistors

“…Among the fundamental components of OTFTs, namely the semiconductor, dielectric, and conductor, studies on the development and application of organic semiconducting materials have intensively been performed for the last few decades [9][10][11][12][13][14][15][16][17][18]. Development of new dielectric materials for OTFTs, which perform as capacitors, insulators, and substrates, is also important to realize various electronic applications based on OTFTs.…”