High Performance OTFTs Fabricated Using a Calamitic Liquid Crystalline Material of 2‐(4‐Dodecyl phenyl)[1]benzothieno[3,2‐b][1]benzothiophene

Abstract

materials have been considered as promising candidates for OTFTs [11][12][13][14][15][16][17] because these materials can form well-ordered polycrystalline thin fi lms with large aligned domains as-deposited or after thermal annealing to promote structuring in liquid-crystalline phases. [18][19][20] Selfassembly with high degrees of intermolecular order facilitates charge transport in organic semiconductors. Recent work has demonstrated the use of a new rod-like liquid-crystalline organic semiconductor,benzothiophene (Ph-BTBT-10), with a highly ordered smectic E (SmE) mesophase for OTFT applications. [ 17 ] Fabricated polycrystalline OTFTs showed mobilities as high as 13.9 cm 2 V −1 s −1 with good thinfi lm uniformity and high thermal durability. [ 17 ] Despite its high performance in OTFTs, Ph-BTBT-10 exhibits a phase transition from its crystalline phase to its SmE phase at around 140 °C; above which the mobility of Ph-BTBT-10-based OTFTs decreases drastically. However, the thermal stability is indispensable to the liquid crystals in OTFT applications. Meanwhile, a simple synthetic route for large-scale production has to be also considered to maintain the low-cost aspects of OTFTs.In this paper, we focus on the investigation of an airstable, rodlike, liquid-crystalline molecular semiconductor,. Unlike Ph-BTBT-10, which only exhibits one ordered liquid-crystalline phase (SmE phase), C12-Ph-BTBT shows three liquid-crystalline phases, including a more ordered smectic X (SmX) phase (X = K or H). Interestingly, structural characterizion by X-ray diffraction (XRD), grazing-incidence X-ray diffraction (GIXD), and atomic force microscopy (AFM) reveals that while the as-deposited C12-Ph-BTBT thin fi lms exhibit a unilamellar structure, they transition to a bilayer polycrystalline structure after annealing at the temperatures of the SmX and the SmE phases. Devices with the highest mobility (8.7 cm 2 V −1 s −1 ) are obtained when C12-Ph-BTBT thin fi lm is annealed at its SmX phase. Though this rodlike liquid-crystalline family of C12-Ph-BTBT has been patented, [ 21 ] its charge transport characteristics in the different smectic phases, especially in the SmX phase, has not been systematically investigated.Here, we elucidate the liquid-crystalline behavior of C12-Ph-BTBT and its effects on the performance of C12-Ph-BTBT-based , 2-(4-dodecyl phenyl)[1] benzothieno[3,2-b ]benzothiophene (C12-Ph-BTBT), is designed with a highly ordered smectic X (SmX) (X = K or H) phase demonstrating high charge-carrier mobility and thermal stability in thin-fi lm transistors. Organic thin-fi lm transistors show mobilities as high as 8.7 cm 2 V −1 s −1 when the C12-Ph-BTBT thin fi lm is annealed at its SmX phase before the electrode deposition. Structural characterization reveals that the as-deposited C12-Ph-BTBT thin fi lms adopt a unilamellar structure. On the other hand, after polycrystalline thin fi lms of C12-Ph-BTBT exhibit bilayer structure after annealing at the temperature of the SmX and the smectic E phases. The highest charge-carri...

Nonlinear Nonacenes with a Dithienothiophene Substructure: Multifunctional Compounds that Act as Columnar Mesogens, Luminophores, π Gelators, and p‐Type Semiconductors

“…The design of novel π‐conjugated polycyclic cores is therefore the key to improve the performances of liquid‐crystalline (LC) semiconductors. In the last decade, LCs based on fused‐thiophene subunits have been flourishing, and organic mesogenic derivatives of oligothiophenes, thienothiophenes (TT), dithienothiophenes (DTT), benzothiophenes (BT), benzotrithiophenes (BTT), benzothieno[3,2‐b]benzothiophene (BTBT), materials have been amply reported. Such compounds exhibit high charge mobility with usual rates up to about 10 cm 2 V −1 s −1 for a rod‐like mesogen and nearly 0.2 cm 2 V −1 s −1 for a discotic mesogen, in their highly ordered crystalline phases, directly obtained after annealing from their mesomorphic temperatures and slowly cooled down.…”

Blending crystalline/liquid crystalline small molecule semiconductors: A strategy towards high performance organic thin film transistors

“…The synthesis of these two materials and their other physicochemical properties are reported elsewhere. 18 As seen from the DSC curve, C12-Ph-BTBT exhibits many smectic phases. We exploited the smectic phase between 65.5 C and 135.2 C in this study.…”

Heterocycle Effects on the Liquid Crystallinity of Terthiophene Analogues

“…Although columnar phases have been the most commonly explored liquid crystalline semiconductors, their one dimensional charge conduction is highly susceptible to defects [38,39,40,41,42,43,44]. More recently, smectic LCs have emerged as more attractive candidate materials since their layered structure permits conduction in two dimensions, potentially leading to more consistent performance [45,46,47,48,49]. Simultaneously tuning both the opto-electronic properties and self-assembly of smectic LC materials represents an ongoing challenge in their exploitation as organic semiconductors.…”