Organic Complementary Inverter Circuits Fabricated with Reverse Offset Printing

Abstract

OTFT technology has the potential to produce integrated circuits such as microprocessors [24] and amplifier circuits [25] with high mechanical flexibility. In particular, complementary integrated circuits combining both p-type and n-type OTFT devices possess many advantages including low power consumption in steady state operation, full-swing logic circuit output, and high noise margin. For these reasons, realizing complementary integrated circuits using reverse offset printing is highly desired, although the fabrication processes and device structures for them have not been fully established.In this study, we demonstrate organic complementary inverter circuits with a stacked structure using fully printed electrodes formed with reverse offset printing. Reverse offset printing and a silver nanoparticle inks sinterable at low temperature were adopted for the precise patterning of source, drain (S/D), and gate electrodes. The p-type and n-type semiconductor layers were also fabricated from solution, and exhibited effective mobilities of 0.41 and 0.2 cm 2 V −1 s −1 , respectively. The complementary inverter circuits using these OTFTs operated at a low supply voltage of 2.5 V with a gain of 14 and achieved high signal gain up to 25 at supply voltage 10 V.The silver (Ag) electrodes were patterned on a glass substrate using reverse offset printing with the process flow depicted in Figure 1a. There are three main steps in the reverse offset printing process: coating, patterning, and transfer. First, the silver ink was coated on the polydimethylsiloxane blanket with a slit coater (step 1: coating). Next, the unnecessary areas were removed from the blanket with a glass printing plate (step 2: patterning). Finally, the silver ink on the blanket was transferred to the substrate (step 3: transfer). Two kinds of silver nanoparticle inks sinterable at 120 °C were used for the source and drain (RAGT-36, DIC) and gate (RAGT-28, DIC) electrodes. Since the drying time between each step is an important factor for realizing high-resolution patterns, [22] the drying time was optimized for Ag nanoparticles. The thickness of the silver layers was controlled by the coating speed in the Step 1.The surface profile and the patterning resolution of the printed electrodes were evaluated using a stylus-type surface profiler (Dektak XT, Bruker) and an optical microscope. The cross-sectional profile (Figure 1b) indicates that the printed electrodes had uniform thicknesses of 100 nm, a flat top p-Type and n-type organic thin film transistors (OTFTs) and complementary inverter circuits with finely patterned electrodes are fabricated by reverse offset printing. The electrodes achieve a channel length of less than 3 µm under optimized printing conditions. High-performance OTFTs are fabricated using these electrodes and printed p-type and n-type organic semiconductors, each achieving a mobility of 0.2 cm 2 V −1 s −1 at a channel length of 50 µm. A complementary inverter circuit fabricated with a stacked OTFT structure is demonstrated using reverse o...

Printed 5-V organic operational amplifiers for various signal processing

“…Note that our organic OPAs were operated at 5 V, whereas the reported ones were operated at 40 V. Since the cut-off frequency of the transistors is usually proportional to the supply voltage, f c = µ V /2π L ( L + Δ L ), the GB product is expected to increase at higher supply voltage. Further improvements of the GB product can be expected if we can reduce the channel length L and overlap length Δ L , for example, by finer printing methods such as reverse-offset printing 27 .

Figure 4 Frequency characteristics of the organic OPAs.

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Printed Organic Transistor-based Biosensors for Non-invasive Sweat Analysis

“…6(b)). 134,135 There are three main steps in the reverse offset printing process: coating, patterning, and transfer. First, ink is coated onto a silicone-based blanket with a slit coater.…”

Printed Organic Complementary Inverter with Single SAM Process Using a p-type D-A Polymer Semiconductor

“…Figure 2b shows a microscope image of the fabricated complementary organic inverter circuit. In previous research, we adopted a stacked device structure to surface-functionalize the source/drain electrodes of p-type and n-type OTFTs with SAM materials separately [15][16][17][18][19]. However, this led to an increase in the number of device manufacturing steps and a reduction in yield.…”

“…In this paper, complementary organic integrated circuits were demonstrated using p-type semiconductors, which are not significantly affected by the work function of the source and drain electrodes. The fabrication process used in this study was reduced in steps to about half compared with the complementary circuit using a stacked structure [15][16][17][18][19]. Further, the dynamic characteristics of the inverter circuit were evaluated using a five-stage ring oscillator.…”