Abstract
The low mobility and large contact resistance in organic thin-film transistors (OTFTs) are the two major limiting factors in the development of high-performance organic logic circuits. Here, solution-processed high-performance OTFTs and circuits are reported with a polymeric gate dielectric and 6,6 bis (trans-4-butylcyclohexyl)-dinaphtho[2,1-b:2,1-f]thieno[3,2-b]thiophene (4H–21DNTT) for the organic semiconducting layer. By optimizing and controlling the fabrication conditions, a high saturation mobility of 8.8 cm2 V−1 s−1 was demonstrated as well as large on/off ratios (> 106) for relatively short channel lengths of 15 μm and an average carrier mobility of 10.5 cm2 V−1 s−1 for long channel length OTFTs (> 50 μm). The pseudo-CMOS inverter circuit with a channel length of 15 μm exhibited sharp switching characteristics with a high signal gain of 31.5 at a supply voltage of 20 V. In addition to the inverter circuit, NAND logic circuits were further investigated, which also exhibited remarkable logic characteristics, with a high gain, an operating frequency of 5 kHz, and a short propagation delay of 22.1 μs. The uniform and reproducible performance of 4H–21DNTT OTFTs show potential for large-area, low-cost real-world applications on industry-compatible bottom-contact substrates.
Highlights
The low mobility and large contact resistance in organic thin-film transistors (OTFTs) are the two major limiting factors in the development of high-performance organic logic circuits
Parylene C was selected as the organic gate dielectric layer because it is well known for its environmental stability, low dielectric constant, low defect density, and optimal surface energy for solution shearing with many solvents, and is an appropriate selection for bottom gate OTFT configuration[13,31,32]
We have successfully demonstrated 4H–21DNTT bottom-contact OTFTs fabricated on flexible (PEN) and glass substrates with a low contact resistance of 1 kΩcm, and we recorded a high mobility of 8.8 cm2 V−1 s−1 for a short channel length of 15 μm
Summary
The low mobility and large contact resistance in organic thin-film transistors (OTFTs) are the two major limiting factors in the development of high-performance organic logic circuits. For solution-processable devices, it is challenging to control parameter variation, in this work we report that optimized solution shearing leads to uniform crystalline films of 4H–21DNTT This allowed us to achieve an average mobility of 6.4 cm2 V−1 s−1 with a small standard deviation of 1.2 for a 15 μm channel length (L) BG-BC OTFT (Fig. 5e). The inverter and NAND logic circuits were fabricated on glass and flexible substrates using solution sheared highly uniform and crystalline 4H–21DNTT films. This combination of high-performance short-channel devices with small gate-to-contact overlap ( LOV) and optimized fabrication conditions was instrumental in achieving improved organic logic circuit performance. The NAND logic circuit demonstrated sharp input–output characteristics and stable operation at a frequency of 5 kHz and a VDD of 20 V
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