Organic Complementary Logic Research Articles

Electrohydrodynamic‐Printed Polyvinyl Alcohol‐Based Gate Insulators for Organic Integrated Devices

Organic printable dielectric layers are required for next‐generation electronic circuits, particularly those used as gate insulators (GIs) in organic field‐effect transistors (OFETs). Herein, optimized electrohydrodynamic (EHD) jet printing with an electrostatic force‐assisted mode is suggested for the fabrication of polyvinyl alcohol (PVA)‐based dielectric patterns after careful consideration of the ink system. The PVA molecules maintain good solubility in polar solvents, even when a crosslinking agent is added, which enables a continuous PVA jet stream with a width smaller than the diameter of the nozzle to be stably obtained. Subsequent EHD printing produces uniform PVA patterns with a smooth surface morphology suitable for the crystal growth of overlying organic semiconductors. The addition of a crosslinking agent in PVA results in direct GI patterns that exhibit superior insulating properties with high dielectric strength as compared with PVA without crosslinking agents. The OFETs with PVA‐based GIs prepared with EHD printing show stable operation with low gate leakage currents. In addition, the feasibility of EHD‐printed PVA layers is demonstrated for application as GIs in organic complementary logic gates.

Ambipolar Conjugated Polymers with Ultrahigh Balanced Hole and Electron Mobility for Printed Organic Complementary Logic via a Two-Step CH Activation Strategy.

High mobility ambipolar conjugated polymers are seriously absent regardless their great potential for flexible and printed plastic devices and circuits. Here, ambipolar polymers with ultrahigh balanced hole and electron mobility are developed via a two-step CH activation strategy. Diketopyrrolopyrrole-benzothiadiazole-diketopyrrolopyrrole (DBD) and its copolymers with thiophene/selenophene units (short as PDBD-T and PDBD-Se) are used as examples. PDBD-Se exhibits highly efficient ambipolar transport with hole and electron mobility up to 8.90 and 7.71 cm2 V-1 s-1 in flexible organic field-effect transistors, presenting a milestone for ambipolar copolymer screening. Based on this performance metrics and good solubility, PDBD-Se is investigated as inkjet-printable semiconductor ink for organic complementary logic circuits. Under ambient processing, maximum hole and electron mobilities reach 6.70 and 4.30 cm2 V-1 s-1 , respectively. Printed complementary inverter and NAND gates with transition voltages near VDD /2 are fabricated, providing an easy-handling, general material for printed electronics and logic.

Controllable Threshold Voltage in Organic Complementary Logic Circuits with an Electron-Trapping Polymer and Photoactive Gate Dielectric Layer.

We present controllable and reliable complementary organic transistor circuits on a PET substrate using a photoactive dielectric layer of 6-[4'-(N,N-diphenylamino)phenyl]-3-ethoxycarbonylcoumarin (DPA-CM) doped into poly(methyl methacrylate) (PMMA) and an electron-trapping layer of poly(perfluoroalkenyl vinyl ether) (Cytop). Cu was used for a source/drain electrode in both the p-channel and n-channel transistors. The threshold voltage of the transistors and the inverting voltage of the circuits were reversibly controlled over a wide range under a program voltage of less than 10 V and under UV light irradiation. At a program voltage of -2 V, the inverting voltage of the circuits was tuned to be at nearly half of the supply voltage of the circuit. Consequently, an excellent balance between the high and low noise margins (NM) was produced (64% of NMH and 68% of NML), resulting in maximum noise immunity. Furthermore, the programmed circuits showed high stability, such as a retention time of over 10(5) s for the inverter switching voltage. Our findings bring about a flexible, simple way to obtain robust, high-performance organic circuits using a controllable complementary transistor inverter.

Reliability study of organic complementary logic inverters using constant voltage stress

We performed constant voltage stresses with different bias conditions on all-organic complementary inverters. We found a 20% maximum variation of DC inverter parameters after a 104-s stress. However, the largest stress-induced degradation was found in the delay times, which increased by a factor as high as 7. This is mainly due to the threshold voltage variation of the p-type thin-film-transistor and the mobility reduction of the n-type thin-film transistors, which both decrease the saturation drain current.

Scaling down of organic complementary logic gates for compact logic on foil

In this work, we realize complementary circuits with organic p-type and n-type transistor integrated on polyethylene naphthalate (PEN) foil. We employ evaporated p-type and n-type organic semiconductors spaced side by side in bottom-contact bottom-gate coplanar structures with channel lengths of 5μm. The area density is 0.08mm2 per complementary logic gate. Both p-type and n-type transistors show mobilities >0.1cm2/Vs with Von close to zero volt. Small circuits like inverters and 19-stage ring oscillators (RO) are fabricated to study the static and the dynamic performance of the logic inverter gate. The circuits operate at Vdd as low as 2.5V and the inverter stage delay at Vdd=10V is as low as 2μs. Finally, an 8bit organic complementary transponder chip with data rate up to 2.7kbits/s is fabricated on foil by successfully integrating 358 transistors.

Organic Complementary Logic Circuits and Volatile Memories Integrated on Plastic Foils

This paper presents organic based logic and memory circuits. All those circuits are made with organic N- and P-type transistors. Organic complementary NAND and NOR gates were characterized and show performance equivalent to or better than the literature-reported ones. The presented memory circuits include an SRAM memory point and an edge-triggered flip-flop. The flip-flop is made of six organic two-input and three-input NAND gates, representing a total of 26 organic transistors for a surface of 170 mm2. The maximum operating frequency of this flip-flop is 220 Hz under a supply of ±20 V. All the circuits were manufactured using a standard organic sheet-to-sheet process in ambient air. Electrical characteristics remain identical after repeated measurements. Finally, a model matching the presented circuits' behavior was carried out, permitting the design of more complex circuits.

Soluble fullerene derivatives: The effect of electronic structure on transistor performance and air stability

The family of soluble fullerene derivatives comprises a widely studied group of electron transporting molecules for use in organic electronic and optoelectronic devices. For electronic applications, electron transporting (n-channel) materials are required for implementation into organic complementary logic circuit architectures. To date, few soluble candidate materials have been studied that fulfill the stringent requirements of high carrier mobility and air stability. Here we present a study of three soluble fullerenes with varying electron affinity to assess the impact of electronic structure on device performance and air stability. Through theoretical and experimental analysis of the electronic structure, characterization of thin-film structure, and characterization of transistor device properties we find that the air stability of the present series of fullerenes not only depends on the absolute electron affinity of the semiconductor but also on the disorder within the thin-film.

Air-stable ambipolar organic field effect transistors with heterojunction of pentacene and N,N′ -bis(4-trifluoromethylben-zyl) perylene-3,4,9,10-tetracarboxylic diimide

Fabrication of ambipolar organic field-effect transistors (OFETs) is essential for the achievement of an organic complementary logic circuit. Ambipolar transports in OFETs with heterojunction structures are realized. We select pentacene as a P-type material and N,N′-bis(4-trifluoromethylben-zyl)perylene-3,4,9,10-tetracarboxylic diimide (PTCDI-TFB) as a n-type material in the active layer of the OFETs. The field-effect transistor shows highly air-stable ambipolar characteristics with a field-effect hole mobility of 0.18 cm2/(V.s) and field-effect electron mobility of 0.031 cm2/(V.s). Furthermore the mobility only slightly decreases after being exposed to air and remains stable even for exposure to air for more than 60 days. The high electron affinity of PTCDI-TFB and the octadecyltrichlorosilane (OTS) self-assembly monolayer between the SiO2 gate dielectric and the organic active layer result in the observed air-stable characteristics of OFETs with high mobility. The results demonstrate that using the OTS as a modified gate insulator layer and using high electron affinity semiconductor materials are two effective methods to fabricate OFETs with air-stable characteristics and high mobility.

N-type organic field-effect transistor using polymeric blend gate insulator with controlled surface properties

Fabrication of n-type organic thin-film transistors (OTFTs) based on organic semiconductor and organic gate insulator is essential for the achievement of organic complementary logic circuit. This article deals with n-type OTFTs with copper hexadecafluorophthalocyanine (F16CuPc) and polymeric blend as an active semiconductor and a gate insulator, respectively. The gate insulator was prepared by blending poly(amic acid) and soluble polyimide with long alkyl side chains (C18 group), which make the surface of the gate insulator more hydrophobic. In order to reduce properties mismatch at interface between F16CuPc and the gate insulator, surface tension of the gate insulator was controlled to 39.1 dyn/cm, which is similar to that of F16CuPc (36.9 dyn/cm). AFM and X-ray diffraction measurements indicated that F16CuPc deposited on the gate insulator showed worm-like flat lying crystal and was highly ordered with a peak of 6.12°. The F16CuPc OTFTs with the gate insulator function as n-channel accumulation mode and their performance was better than that of F16CuPc OTFTs with SiO2, demonstrating its potential applications for flexible organic display. Charge carrier field-effect mobility, ION/IOFF, and subthreshold slope of the OTFT were 6 × 10−3 cm2/V s, 5.4 × 103, and 7.3 V/dec, respectively.