Metal and metalloid phthalocyanines are an abundant and established class of materials widely used in the dye and pigment industry as well as in commercial photoreceptors. Silicon phthalocyanines (SiPcs) are among the highest-performing n-type semiconductor materials in this family when used in organic thin-film transistors (OTFTs) as their performance and solid-state arrangement are often increased through axial substitution. Herein, we study eight axially substituted SiPcs and their integration into solution-processed n-type OTFTs. Electrical characterization of the OTFTs, combined with atomic force microscopy (AFM), determined that the length of the alkyl chain affects device performance and thin-film morphology. The effects of high-temperature annealing and spin coating time on film formation, two key processing steps for fabrication of OTFTs, were investigated by grazing-incidence wide-angle X-ray scattering (GIWAXS) and X-ray diffraction (XRD) to elucidate the relationship between thin-film microstructure and device performance. Thermal annealing was shown to change both film crystallinity and SiPc molecular orientation relative to the substrate surface. Spin time affected film crystallinity, morphology, and interplanar d-spacing, thus ultimately modifying device performance. Of the eight materials studied, bis­(tri-n-butylsilyl oxide) SiPc exhibited the greatest electron field-effect mobility (0.028 cm2 V–1 s–1, a threshold voltage of 17.6 V) of all reported solution-processed SiPc derivatives.

Silicon and tin­(IV) phthalocyanines, which have been demonstrated as simple-to-synthesize materials for n-type organic thin-film transistors (OTFTs), have relatively shallow lowest unoccupied molecular orbital (LUMO) levels that create a Schottky barrier with the gold source–drain contacts typically used in device fabrication. To reduce the contact resistance (R C) associated with this barrier and improve the OTFT performance, we fabricated bottom-gate top-contact (BGTC) devices using low-work-function metals (Mn/Cr) and an electron dopant material (bathocuproine, BCP) as contact interlayers. We characterized two tin phthalocyanines (SnPcs), tin bis­(pentafluorophenoxy)­phthalocyanine (F10-SnPc) and tin bis­(2,4,6-trifluorophenoxy)­phthalocyanine (246F-SnPc), as organic semiconductors (OSCs) and compared them to their silicon phthalocyanine (SiPc) analogues. We found that using Mn and Cr interlayers with SiPc OTFTs reduces R C to as low as 11.8 kΩ cm and reduces the threshold voltage (V T) to as low as 7.8 V while improving linear region characteristics compared to devices using silver or gold electrodes only. BCP interlayers appear to reduce V T in all SiPc and SnPc devices and increase the off-state conductivity of SnPc devices if covering the entire OSC. Overall, this work demonstrates the potential for metal interlayers and solid-state organic interlayers for improving electron transport in low-cost, n-type OTFTs using group 14 phthalocyanines.

Silicon phthalocyanines (SiPcs) have shown great potential as n-type or ambipolar organic semiconductors in organic thin-film transistors (OTFTs) and organic photovoltaics. Although properly designed SiPcs rival current state-of-the-art n-type organic semiconducting materials, relatively few structure–property relationships have been established to determine the impact of axial substituents on OTFT performance, hindering the intelligent design of the next generation of SiPcs. To address this omission, we have developed structure–property relationships for vapor-deposited SiPcs with phenoxy axial substituents. In addition to thorough electrical characterization of bottom-gate top-contact OTFTs, we extensively investigated SiPc thin films using X-ray diffraction, atomic force microscopy (AFM), grazing-incidence wide-angle X-ray scattering (GIWAXS), and density functional theory (DFT) modeling. OTFT performance, including relative electron mobility (μe) of materials, was in general agreement with values obtained through DFT modeling including reorganization energy. Another significant trend observed from device performance was that increasing the electron-withdrawing character of the axial pendant groups led to a reduction in threshold voltage (V T) from 47.9 to 21.1 V. This was corroborated by DFT modeling, which predicted that V T decreases with the square of the dipole induced at the interface between the SiPc pendant and substrate. Discrepancies between modeling predictions and experimental results can be explained through analysis of thin-film morphology and orientation by AFM and GIWAXS. Our results demonstrate that a combination of DFT modeling to select prospective candidate materials, combined with appropriate processing conditions to deposit molecules with a favorable thin-film morphology in an “edge-on” orientation relative to the substrate, yields high-performance n-type SiPc-based OTFTs.

Suitably modified linear conjugated poly(arylene ethynylene)s are able to assist effective debundling and dispersion of crude as-prepared single-walled carbon nanotube powders in organic solvents, the dispersion of which is effected via a surface coating mechanism and, to some extent, in a size-selective fashion.

chemical and physical properties, including high mechanical strength, flexi bility, and unique optical and electrical properties. [1,2] The flexibility and stretch ability of carbon nanotubes, combined with their potential for comparable elec trical performance to traditional rigid materials (such as polysilicon and metal oxides) makes them particularly attractive for applications in wearable electronics, prosthetics, and flexible and printed elec tronics. [3] Their capacity for high charge carrier mobilities, [4] combined with solu tion processability, has resulted in the incorporation of SWNTs into photovol taics, [5] field effect transistors, [6] chem ical and biological sensors, [7][8][9] logic circuits, [10,11] and infrared photodetectors for telecommunications. [12] The structural polydispersity of as synthesized SWNTs, both in atomic struc ture and length, remains a major issue hindering widespread applications of these materials into electronics devices. [13] While some synthetic control over the diameter distribution can be achieved, all common techniques produce a dis tribution of chiralities and a mixture of both metallic and semiconducting nano tubes. [14] These mixtures are normally comprised of a ratio of ≈2:1 semiconducting SWNTs (scSWNTs) to metallic SWNTs (mSWNTs), in addition to the retention of impurities such as catalyst particles and amorphous carbon. This disparity in terms of electrical properties is not suitable for organic elec tronic devices, as mSWNTs can act as percolating or directly bridging paths that electrically short SWNT transistors, making the isolation of pure scSWNTs from a raw mixture of the utmost importance. [15] Additionally, SWNTs have poor solu bility and require the introduction of ancillary dispersants to properly exfoliate tube bundles to allow for the fabrication of uniform networks.Significant progress in the dispersion and separation of SWNTs according to electronic character, [16] chirality, [17] diameter, [18] or length [19] has been made over the past two decades. Density gradient ultracentrifugation, [20] gel chromatography, [21] DNA wrapping combined with ion The realization of organic thin film transistors (OTFTs) with performances that support low-cost and large-area fabrication remains an important and challenging topic of investigation. The unique electrical properties of singlewalled carbon nanotubes (SWNTs) make them promising building blocks for next generation electronic devices. Significant advances in the enrichment of semiconducting SWNTs, particularly via π-conjugated polymers for purification and dispersal, have allowed the preparation of high-performance OTFTs on a small scale. The intimate interaction of the conjugated polymer with both SWNTs and the dielectric necessitates the investigation of a variety of conjugated polymer derivatives for device optimization. Here, the preparation of polymer-SWNT composites containing carbazole moieties, a monomer unit that has remained relatively overlooked for the dispersal of large-diameter semiconducting...