Blending effect of 6,13-bis(triisopropylsilylethynyl) pentacene–graphene composite layers for flexible thin film transistors with a polymer gate dielectric

Abstract

Solution processible poly(4-vinylphenol) is employed as a transistor dielectric material for low cost processing on flexible substrates at low temperatures. A 6,13-bis (triisopropylsilylethynyl) (TIPS) pentacene-graphene hybrid semiconductor is drop cast to fabricate bottom-gate and bottom-contact field-effect transistor devices on flexible and glass substrates under an ambient air environment. A few layers of graphene flakes increase the area in the conduction channel, and form bridge connections between the crystalline regions of the semiconductor layer which can change the surface morphology of TIPS pentacene films. The TIPS pentacene-graphene hybrid semiconductor-based organic thin film transistors (OTFTs) cross-linked with a poly(4-vinylphenol) gate dielectric exhibit an effective field-effect mobility of 0.076 cm(2) V(-1) s(-1) and a threshold voltage of -0.7 V at V(gs) = -40 V. By contrast, typical TIPS pentacene shows four times lower mobility of 0.019 cm(2) V(-1) s(-1) and a threshold voltage of 5 V. The graphene/TIPS pentacene hybrids presented in this paper can enhance the electrical characteristics of OTFTs due to their high crystallinity, uniform large-grain distribution, and effective reduction of crystal misorientation of the organic semiconductor layer, as confirmed by x-ray diffraction spectroscopy, atomic force microscopy, and optical microscopy studies.

Supramolecular Approaches to Graphene: From Self‐Assembly to Molecule‐Assisted Liquid‐Phase Exfoliation

“…It is, however, important to note that blends feature mayor drawbacks such as phase segregation, [261] graphene random aggregation, [262] cristallinity loss in the semiconductor matrix [263] and very poor control over graphene deposition. [264] In 2015 we demonstrated [265] an alternative strategy to fabricate multifunctional graphene-polymer hybrid thin-film transistors (PG-TFT) whose transport properties are tunable by varying the deposition conditions of graphene dispersions prepared by the means of UILPE of graphite in NMP.…”

Ultrathin polycrystalline 6,13-Bis(triisopropylsilylethynyl)-pentacene films

“…[4][5][6][7] Some group have tried mixing TIPS-P with other components, like graphene flakes, to modify the crystallization and performance of TIPS-P films. 8 A high hole mobility of 0.8-4.6 cm 2 V À1 s…”

“…8 However, these methods require additional processing that is not fully compatible with mass production. For this reason, they are less desirable for practical device applications that demand simple, low-cost fabrication.…”

Graphene exfoliation in the presence of semiconducting polymers for improved film homogeneity and electrical performances

“…[17] Graphene would benefit greatly from these characteristics, and because of this reason several attempts of combining these two types of materials have been reported in the literature. [18][19][20][21][22][23][24][25] These include multi-step procedures based on the subsequent deposition of a graphene and the polymeric semiconductor via spin-coating, ink-jet printing or thermal evaporation. [22,23,26] In particular, Torrisi and co-workers fabricated the active channel of a transistor by successive printing of graphene ink and poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene (PQT-12), reaching high electrical performances (mobility of 100 cm²/Vs).…”

“…[18,24,25] In particular, it was recently demonstrated that liquid-phase exfoliated graphene can be codeposited with a polymeric semiconductor and used in thin-film transistors in order to boost the ambipolar character of the polymer. [18] While this method is interesting, it does suffer from several drawbacks, including phase segregation between the two components, [18] graphene random aggregation, [19] crystallinity loss in the semiconductor matrix [20] and poor control over graphene deposition. [21] One interesting approach could rely on the simultaneous blending of the OSCs with graphene during sonication-assisted exfoliation of graphite powder into graphene nanosheets, with OSCs acting as a dispersion stabilizing agents (DSAs) and preventing the re-aggregation of the exfoliated graphene flakes, ultimately enabling the production of homogeneous bicomponent dispersions.…”