Enhancement of Interconnectivity in the Channels of Pentacene Thin‐Film Transistors and Its Effect on Field‐Effect Mobility

Abstract

With the aim of improving the field‐effect mobility of transistors by promoting the interconnectivity of the grains in pentacene thin films, deposition conditions of the pentacene molecules using one‐step (total thickness of layer 50 nm: 0.1 Å s–1) and two‐step (first layer 10 nm: 0.1 Å s–1, second layer 40 nm: 4.0 Å s–1) depositions are controlled. Significantly, it is found that the continuities of the pentacene thin films vary with the deposition conditions of the pentacene molecules. Specifically, a smaller number of voids is observed at the interface for the two‐step deposition, which results in field‐effect mobilities as high as 1.2 cm2 V–1 s–1; these are higher by more than a factor of two than those of the pentacene films deposited in one step. This remarkable increase in field‐effect mobility is due in particular to the interconnectivity of the pentacene grains near the insulator substrate.

Phenacyl–Thiophene and Quinone Semiconductors Designed for Solution Processability and Air‐Stability in High Mobility n‐Channel Field‐Effect Transistors

“…The red solid obtained upon filtration and concentration was purified by column chromatography on silica gel to afford 3.19 g of 19 as a red solid that was dried in vacuo and used immediately in the next reaction. Elemental analysis (%) calcd C 10 Synthesis of 2,7-diiodo-9,10-phenanthrenequinone (22): Iodine (14.6 g, 57.5 mmol) and potassium permanganate (10.3 g, 65.0 mmol) were suspended in a mixture of 100 mL glacial acetic acid and 30 mL acetic anhydride that had been stirring for 5 h. The suspension was stirred vigorously with a magnetic stirbar and maintained at 5 8C while H 2 SO 4 (aq, conc., 40 mL) was added dropwise (CAUTION: addition of concentrated H 2 SO 4 can produce a vigorous exotherm if not performed slowly). The slurry was then allowed to warm to room temperature before phenanthrenequinone (10.4 g, 50.0 mmol) was added and the reaction mixture stirred for 2 days.…”

“…All that is clear is that the addition of highly lipophilic substituents to conjugated cores promotes the formation of uniform, textured films, which are essential for device performance. [9] Several studies have addressed the importance of gate dielectric surface functionalization, attempting to rationalize the effects of surface energy, roughness, chemistry, [10][11][12] and more recently, viscoelastic properties, [13] on OSC film growth, morphology, and ultimately carrier mobility patterns. Enhanced OSC film morphology and microstructure can also be achieved using a variety of techniques, including substrate rubbing/alignment layers, magnetic fields, layer-by-layer film deposition, vitrification agents, zone casting, zone refining, and solvent vapor annealing.…”

Effect of the hydrophobicity and thickness of polymer gate dielectrics on the hysteresis behavior of pentacene-based field-effect transistors

“…5,6 Such high device performances have been achieved by carefully controlling the growth of the pentacene film via surface treatment on the gate dielectrics and optimization of the processing parameters ͑e.g., deposition rate and substrate temperature͒. [7][8][9] Also, the development of gate dielectrics with a high capacitance-which could be achieved by reducing the thickness of the dielectric and/or increasing the dielectric constant-could lead to lower operating voltages of the OFETs ͑i.e., below a few volts͒. [10][11][12][13][14] However, the hysteresis effect observed during device operation diminishes the practical utility of OFETs.…”

Low temperature processed bilayer dielectrics for low-voltage flexible saturated load inverters

“…The results agree well with the improvement in the charge carrier mobility on ODPA/ Al 2 O 3 and show that the medium size pentacene grains have good interconnection. 10,13,14 In addition, we investigated the mechanical flexibility of the switching transistors. The measurements were done before, during and after bending the devices with controlled bending strains.…”