Self-Assembled Monolayers Made of 6-(5-((6-((5-hexylthiophen-2-yl)ethynyl)-9,10-bis(phenylethynyl)anthracen-2-yl)ethynyl)thiophen-2-yl)hexyl 3-(Triethoxysilyl)Propylcarbamate for Ultrathin Film Transistors

Abstract

A new functionalized triethoxysilane bearing an X-shaped, anthracene-based semiconducting molecule on one arm was designed and synthesized as a precursor for the preparation of a self-assembled monolayer (SAM) on a SiO(2) substrate. 3-Isocyanatopropyl triethoxysilane was reacted with a monohydroxyl-terminated X-shaped, anthracene-based semiconducting molecule in the presence of tin catalyst. The 6-(5-((6-((5-hexylthiophen-2-yl)ethynyl)-9,10-bis(phenylethynyl)anthracen-2-yl)ethynyl)thiophen-2-yl)hexyl 3-(triethoxysilyl)propylcarbamate (BATHT-TEOS) was found to be stable and sufficiently reactive to form organic monolayers on hydroxylated SiO(2) surfaces. The structures and properties of these SAMs were investigated using X-ray photoelectron spectroscopy, UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, laser scanning confocal microscopy-PL spectrometry, and spectroscopic ellipsometry. In this work, BATHT-SAM was employed as an interfacial layer on SiO(2) to fabricate ultrathin film transistors (UTFTs, active layer thickness ∼ 16.09 nm). The device UTFT-I, made of 0.06 wt % 5,5'-(9,10-bis(phenylethynyl)anthracene-2,6-diyl)bis(ethyne-2,1-diyl)bis(2-hexylthiophene) (BATHT) solution on an n-octyltrichlorosilane-SAM/SiO(2) layer, showed no gate effect for the carrier transport behavior; however, the device UTFT-II, fabricated on BATHT-SAM/SiO(2), exhibited field effect mobilities of 0.04 cm(2) V(-1) s(-1) (I(on/off) ∼ 6.3 × 10(3) to 1.0 × 10(4)). This can be attributed to the effect of BATHT-SAM inducing uniform coverage and ordering of BATHT molecules as an upper layer.

Microstructured Ultrathin Organic Semiconductor Film via Dip-Coating: Precise Assembly and Diverse Applications

“…Among these methods, thermal sublimation unavoidably wastes many raw materials and easily yields discontinuous patches or numerous grain boundaries . The LB and covalence-based self-assembly methods generally require special molecular groups, which may compromise the electrical performance. , MASA, blading coating, solution shearing, and dip-coating are simple and efficient solution process methods for fabricating patterned structures or ultrathin film. With comparison to its counterparts, dip-coating has an unparalleled advantage in simultaneously obtaining monolayer-precision ultrathin film and microstructured morphology with high throughput. ,, …”

Directed Orientation of Oligo(phenylene ethynylene)s Using Ureas or Urethanes in Rod–Coil Copolymers

“…Conjugated polymers as well as oligomers, in particular phenylene ethynylene‐based systems, represent a suitable class of materials for optoelectronic devices, e.g., light‐emitting diodes or thin film transistors . Such materials exhibit several benefits such as high charge‐carrier mobility, a small band gap, efficient exciton transfer, and a high quantum yield for fluorescence .…”

Controlled Growth of Ultrathin Film of Organic Semiconductors by Balancing the Competitive Processes in Dip-Coating for Organic Transistors

“…[10][11][12][13][14][15][16] On the other hand, ultrathin film (< 15 nm, Figure 1a) of organic semiconductors represents a kind of nano-scale film consisting of monolayer to few molecular layers (Figure 1b). [17][18][19][20][21][22][23] 3 According to the surface morphology, ultrathin film includes continuous and microstructured film (Figure 1a), both of which provide excellent platform for fundamental researches and practical applications. [24][25][26][27][28][29][30] For example, in organic field-effect transistors (OFETs), the charge transporting layer (conductive channel) is located at the interface between semiconductors and dielectrics, and its thickness is only about one to several nm, i.e., one to several molecular layers.…”

“…Organic semiconductor is the key component of organic electronic devices that possess unique features such as low cost, mechanical flexibility, and large area coverage. − Generally, the thickness of organic semiconductor layer in organic electronic devices is in the range of several tens to hundreds of nanometer (nm), which consists of tens or more molecular layers. − On the other hand, ultrathin film (<15 nm, Figure a) of organic semiconductors represents a kind of nanoscale film consisting of a monolayer to a few molecular layers (Figure b). − According to the surface morphology, ultrathin film includes continuous and microstructured film (Figure a), both of which provide excellent platform for fundamental researches and practical applications. − For example, in organic field-effect transistors (OFETs), the charge transporting layer (conductive channel) is located at the interface between semiconductors and dielectrics, and its thickness is only about one to several nm, i.e., one to several molecular layers. − In the conventional OFETs, conductive channel is buried in the thick organic semiconductor film (tens of nm) and difficult to characterize . If ultrathin film is utilized in OFETs, the conductive channel is exposed outside, which would be favorable for both the investigation of conductive channel and the application for sensors. − However, it is quite difficult to develop a general principle to grow large-area, uniform, and continuous (at least along one dimension) ultrathin film of different organic semiconductors.…”

“…Until now, several methods have been used for the preparation of ultrathin film of organic semiconductors, such as vapor deposition, Langmuir–Blodgett technique, electro-static assembly, covalent self-assembly, dip-coating, and so on. − ,− Generally, in the ultrathin film regime, vapor deposition usually produces the discontinuous patches or nonuniform film consisting of lots of grains and grain boundaries. Langmuir technique, electro-static assembly, and covalent self-assembly usually need the organic semiconductors with some special functional groups such as hydroxyl, silyl, etc., which may influence the electrical performance.…”