Direct
drawing techniques have contributed to the ease of patterning
soft electronic materials, which are the building blocks of analog
and digital integrated circuits. In parallel with the printing of
semiconductors and electrodes, selective deposition of gate insulators
(GI) is an equally important factor in simplifying the fabrication
of integrated devices, such as NAND and NOR gates, and memory devices.
This study demonstrates the fabrication of six types of printed GI
layers (high/low-k polymer and organic–inorganic
hybrid material), which are utilized as GIs in organic field-effect
transistors (OFETs), using the electrostatic-force-assisted dispensing
printing technique. The selective printing of GIs on the gate electrodes
enables us to develop practical integrated devices that go beyond
unit OFET devices, exhibiting robust switching performances, non-destructive
operations, and high gain values. Moreover, the flexible integrated
devices fabricated using this technique exhibit excellent operational
behavior. Therefore, this facile fabrication technique can pave a
new path for the production of practical integrated device arrays
for next-generation devices.
A novel fluorinated organic–inorganic (O–I) hybrid sol—gel based material, named FAGPTi, is successfully synthesized and applied as a gate dielectric in flexible organic thin‐film transistors (OTFTs). The previously reported three‐arm‐shaped alkoxysilane‐functionalized amphiphilic polymer yields a stable O–I hybrid material consisting of uniformly dispersed nanoparticles in the sol‐state. Here, a fluorinated precursor is introduced into the system, making it possible to realize more stable spherical composites. This results in long‐term colloidal stability (≈1.5 years) because composite growth is strongly inhibited by the presence of fluorine groups with intrinsically strong repulsive forces. Additionally, the FAGPTi film is easily deposited via thermally annealed sol–gel reactions; the films can be successfully fabricated through the printing method, and exhibit excellent flexibility and enhanced insulating properties compared to existing materials. OTFTs with FAGPTi layers show highly stable driving characteristics under severe bending conditions (1.9% strain). Integrated logic devices are also successfully operated with these OTFTs. Additionally, it can facilely be applied to amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) TFT devices other than OTFT. Therefore, this synthetic strategy can provide useful insights into the production of functional O–I hybrid materials, enabling the efficient fabrication of electronic materials and devices exhibiting these properties.
A π-conjugated
polymer semiconductor, PBDTTTffPI, was synthesized
for use as an organic semiconductor suitable for electrohydrodynamic
(EHD) jet printing technology. Bulky alkylation of the polymer gave
PBDTTTffPI good solubility in several organic solvents. EHD jet printing
using PBDTTTffPI ink produced direct patterns of polymer semiconductors
while maintaining smooth surface morphologies and crystal structures
similar to those of spin-coated PBDTTTffPI films. EHD-jet-printed
PBDTTTffPI was appropriate for use as a semiconductor layer in organic
field-effect transistors (OFETs) and logic gates. OFETs that used
EHD-jet-printed PBDTTTffPI had better electrical characteristics than
devices that used spin-coated semiconductor films. When a dielectric
material (Al2O3) with a high dielectric constant
was introduced, the jet-printed PBDTTTffPI operated well at low voltages.
Integrated devices such as inverters, NAND gates, and NOR gates were
fabricated by printing PBDTTTffPI patterns and showed good switching
behaviors. Therefore, the use of printable PBDTTTffPI provides an
advance toward fabrication of practical integrated arrays in next-generation
devices.
Solution-based printing has contributed to the facile deposition of various types of materials, including the building blocks of printed electronics. In particular, solution-processable organic semiconductors (OSCs) are regarded as one of the most fascinating candidates for the fabrication of printed electronics. Herein, we report electrohydrodynamic (EHD) jet-printed p-and n-type OSCs, namely 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS−PEN) and 6,13-bis((triisopropylsilyl)ethynyl)-5,7,12,14tetraazapentacene (TIPS−TAP), and their use as single-OSC layers and as OSC mixed p−n layers to fabricate solutionprocessed p-, n-, and ambipolar-type organic field-effect transistors (OFETs). Use of the dragging mode of EHD jet printing, a process driven under a low electrostatic field with a short nozzle-to-substrate distance, was found to provide favorable conditions for growth of TIPS−PEN and TIPS−TAP crystals. In this way, the similar molecular structures of TIPS−PEN and TIPS−TAP yielded a homogeneous solid solution and showed ambipolar transport properties in OFETs. Therefore, the combination of single-and mixed-OSC layers enabled the preparation of various charge-transported devices from unit to integrated devices (NOT, NAND, NOR, and multivalued logic). Therefore, this fabrication technology can be useful for assisting in the production of OSC layers for practical applications in the near future.
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