Marangoni Effect‐Controlled Growth of Oriented Film for High Performance C8‐BTBT Transistors

Abstract

of researchers because of its higher carrier mobility in solution fabricated OFET devices. [5,6] Anthopoulos introduced a method for blending C8-BTBT with a polymer, achieving a mobility of 13 cm 2 V −1 s −1 , while Minemawari et al. reported that the C8-BTBT carrier mobility could reach 16.4 cm 2 V −1 s −1 by applying the inkjet printing process. [7,8] Bao and co-workers reported C8-BTBT transistors with an ultrahigh carrier mobility of 43 cm 2 V −1 s −1 , which were produced by off-center spin coating. [6] Wang et al. used the airflow method to fabricate C8-BTBT single crystalline layers and transistors with average and maximum mobilities of 4.8 and 13.0 cm 2 V −1 s −1 , respectively. [9] Nonetheless, the fabrication methods proposed until now still present the drawbacks of being complex and of producing films characterized by an insufficient mobility and low uniformity when to be applied to large-area substrates. Therefore, new methods for OFETs production still need to be developed.In a previous work, our group achieved the production of highly oriented 6,13-bis(triisopropylsilylethynyl) pentacene crystalline thin films by the Marangoni effect-controlled oriented growth (MOG). [10] The MOG method combines the advantages of the "Coffee ring" and Marangoni effects, including highly oriented film deposition, capability of fabricating high surface area films, and low fabrication times. In this work, the MOG method is extended to the fabrication of a C8-BTBT thin film. The substrate is dipped into a mixture solution of C8-BTBT in methylbenzene and carbon tetrachloride and then lifted from the liquid. With the evaporation of the solvent, the "coffee ring" effect makes C8-BTBT particles deposit on the upper edge of the substrate, while the Marangoni effect causes a movement of the C8-BTBT particle away from the upper edge (Figure 1). The balance of these two effects favors the production of a uniform C8-BTBT film on the substrate during the evaporation of the solution. The produced C8-BTBT film is oriented and uniformly covers the substrate.In our experiments, a glass/indium tin oxide (ITO)/AlO x substrate is used. The choice was made because that AlO x can act as the dielectric gate and is capable of adsorbing the alkyl solution, which is favoring the optimal arrangement of the C8-BTBT molecules based on the MOG method. [11][12][13] Grazing-incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM) were applied to find that the produced C8-BTBT film was highly oriented. The OFETs based on this C8-BTBT Highly oriented organic semiconductors have the advantages of relative low trap density and high carrier mobility. These features make organic transistors valuable in many commercial fields, such as electronic sensor arrays and flexible circuits. Here a simple and efficient "Marangoni effect-controlled growth" method is introduced to fabricate highly oriented 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothiophene (C8-BTBT) films on AlO x substrates. The oriented film can cover nearly 60% of the substra...

Surficial Marangoni Flow‐Induced Growth of Ultrathin 2D Molecular Crystals on Target Substrates

“…On the basis of this in situ observation, we proposed a mechanism to interpret the formation process of the 2DMCs, as shown in Figure 3b-e. After the droplet was cast on the substrate, it would rapidly spread over the whole substrate and form a thin liquid film (Figure 3b). [33,34] In-suit observation of the flow process of the dropped Dif-TES-ADT/toluene solution on the DMF surface further validates this point ( Figure S9 and Movie S2, Supporting Information). Solvents evaporate much faster at the liquid/air interface than that at other areas.…”

“…Since the mixed solvent had a good wettability on the substrate with a low contact angle of ≈2.1° ( Figure S8, Supporting Information), the contact line was strongly pinned by the substrate, which would maintain the shape of the liquid film at the beginning of the crystal growth process. [33,34] Compared with previous works, our Marangoni flow occurred on the surface of antisolvent DMF. [31,32] Compared with DMF, toluene as the good solvent had a lower boiling point than that of DMF, so it would first evaporate at the interface.…”

Scalable Fabrication of Organic Single-Crystalline Wafers for Reproducible TFT Arrays

“…Figure 2a schematically illustrates the growth of an organic single crystal by continuous edge-casting. Generally, for meniscus-guided crystal growth methods, solvent evaporation takes place predominantly at the vapor–liquid interface, resulting in solute supersaturation 16,19,21,22,24 . This initiates molecular aggregation at the surface of the solution and subsequent crystallization on the substrate.…”

“…Particularly in the silicon electronics industry, the ultimate reliability is realized by the use of a single-crystal silicon wafer 10,11 . Recently, various groups have demonstrated the wafer-scale fabrication of ultra-thin single-crystal OSCs via a simple one-shot solution process 12–22 . The resulting excellent electronic properties, such as a field-effect mobility up to 10 cm 2 V −1 s −1 , allow high-speed switching operations at a few tenths of a MHz 16 .…”

Correlation between the static and dynamic responses of organic single-crystal field-effect transistors

“…Following various recent developments in printing technologies and in materials science, the mass production of highly integrated OSC devices is expected to lead to challenges in terms of the internet of things (IoT) challenges [13][14][15] . Recently, various groups have demonstrated the wafer-scale fabrication of ultra-thin single-crystal OSCs via a one-shot solution process [16][17][18][19][20][21][22][23][24][25][26][27] . The resulting excellent electronic properties, including a field-effect mobility up to 10 cm 2 V −1 s −1 originating from coherent band-like transport 20,27,28 , in conjunction with the miniaturization of organic field-effect transistor (OFET) devices, allows high-speed switching operations at a few tens of a MHz 20,29,30 .…”