Organic Complementary Inverters Research Articles

Low-power organic field-effect transistors and complementary inverter based on low-temperature processed Al2O3 dielectric

Organic-based complementary inverter could be a key component in future flexible and portable electronic products, which require low-power operation, high operating stability and flexible compatibility at the same time. A simple method for making excellent Al2O3 gate dielectric is developed toward the target, and it is a low-cost solution process with a low annealing temperature compatible with plastic substrates. Utilizing the Al2O3 dielectric, both p-type and n-type low-voltage organic field-effect transistors (OFETs) are realized. The device operating voltage is down to ±3 V, and the On/Off ratio is up to 106. The hole and electron field-effect mobilities are 2.7 cm2/V and 0.2 cm2/V, respectively, and the subthreshold swing is as small as about 110 mV/decade. The high quality of the Al2O3 dielectric results in high operating stability of the devices. The p-type and n-type OFETs are integrated to achieve a low-power complementary inverter with a large gain, which can be successfully fabricated on a flexible substrate.

Photo-patternable high-k ZrOx dielectrics prepared using zirconium acrylate for low-voltage-operating organic complementary inverters

Solution-processed dielectric materials with a high dielectric constant (k) have attracted considerable attention due to their potential applications in low-voltage-operating organic field-effect transistors (OFETs) for realizing large-area and low-power electronic devices. In terms of device commercialization, the patterning of each film component via a facile route is an important issue. In this study, we introduce a photo-patternable precursor, zirconium acrylate (ZrA), to fabricate photo-patterned high-k zirconium oxide (ZrOx) dielectric layers with UV light. Solution-processed ZrA films were effectively micro-patterned with UV exposure and developing, and transitioned to ZrOx through a sol-gel reaction during deep-UV annealing. The UV-assisted and ∼10 nm-thick ZrOx dielectric films exhibited a high capacitance (917.13 nF/cm2 at 1 KHz) and low leakage current density (10−7 A/cm2 at 1.94 MV/cm). Those films could be utilized as gate dielectric layers of OFETs after surface modification with ultrathin cyclic olefin copolymer layers. Finally, we successfully fabricated organic complementary inverters exhibiting hysteresis-free operation and high voltage gains of over 42 at low voltages of ≤3 V.

A Low‐Voltage Organic Complementary Inverter with High Operation Stability and Flexibility Using an Ultrathin iCVD Polymer Dielectric and a Hybrid Encapsulation Layer

A low-voltage, air-stable, and flexible organic complementary inverter is demonstrated by incorporating an ultrathin polymer gate dielectric and a thin-film encapsulation layer. The inverter exhibits a high gain value of 130V/V at a switching threshold voltage of 1.52 V and a supply voltage as low as 3 V. The device also exhibits high flexibility and long-term air stability.

Solution-Processed Organic Complementary Inverters Based on TIPS-Pentacene and PDI8-CN2

Organic complementary inverter is one of the key building blocks of some organic circuits, and the electrical performance and manufacture technique of inverter may determine its applications prospect. Through solution method, the organic complementary inverters were demonstrated based on triisopropylsilylethynyl-pentacene and N,N’-dioctyl-1,7-dicyano-perylene-(3,4:9,10)-tetracarboxylic diimide, which exhibited low operation voltage (4–10 V), high gain (12–27), large noise margin (>60% of 1/ $2V_{\mathrm {dd}})$ , low static power dissipation (tens of nanowatts), and a propagation delay time of $\sim 0.42$ ms. The solution processibility and overall performance of the inverter are highly promising for the applications in organic circuits.

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.

Cellulose-Derivative-Based Gate Dielectric for High-Performance Organic Complementary Inverters.

been realized using organic thin-fi lm transistors (OTFTs) as the essential element. In the majority of these applications OTFTs are integrated either in the form of arrays or as digital logic. The fundamental building block of digital logic is the inverter, a circuit that inverts an input signal. Much work has been devoted in the last fi ve years to design unipolar inverters using p-typeonly OTFTs. [ 18‐23 ] Unfortunately, unipolar logic based on single gate OTFTs always suffers from high power consumption and low noise margin coupled with high noise margin variability and therefore impedes the fabrication of complex circuits having hundreds or more logic gates. [ 19,22,23 ] In this context, it stands

Hybrid dielectric layer for low operating voltages of transparent and flexible organic complementary inverter

Although flexibility and transparency are considered advantages of organic electronic devices along with low processing cost and the possibility of large-area production, high operating voltages and metallic contacts are obstacles to their application in real electronic products. In this work, flexible and transparent organic complementary inverters that can be operated with low voltage were fabricated on a plastic substrate. Two different air-stable organic semiconductors, fluorinated copper phthalocyanine and pentacene, are used for n-type and p-type transistors, respectively. An ITO gate electrode was deposited by sputtering, and a hybrid dielectric layer with a thin Al2O3 layer and self-assembled monolayers (SAMs) was fabricated to reduce the operation voltage. To confirm the properties of the hybrid dielectric layer, the capacitance and gate leakage current were measured. Then, source and drain electrodes were formed from gold or ITO specifically for fully transparent devices. For the ITO electrodes, a MoO3 interlayer was incorporated between the pentacene and ITO to reduce the contact resistance caused by mismatch of workfunction. Finally, we evaluated the low-voltage operation of the flexible organic inverters and the fully transparent device through transmittance measurement.

Fabrication of a wafer-scale uniform array of single-crystal organic nanowire complementary inverters by nanotransfer printing

Abstract We report the fabrication and electrical characterization of a wafer-scale array of organic complementary inverters using single-crystal 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and fullerene (C60) nanowires as p- and n-channels, respectively. Two arrays of single-crystal organic nanowires were generated consecutively on desired locations of a common substrate with a desired mutual alignment by a direct printing method (liquid-bridge-mediated nanotransfer molding). Another direct printing of silver micron scale structures, as source and drain electrodes, on the substrate with the two printed nanowire arrays produced an array of complementary inverters with a bottom gate, top contact configuration. Field-effect mobilities of single-crystal TIPS-PEN and C60 nanowire field-effect transistors (FETs) in the arrays were uniform with 1.01 ± 0.14 and 0.10 ± 0.01 cm2V−1 s−1, respectively. A wafer-scale array of complementary inverters produced all by the direct printing method showed good performance with an average gain of 25 and with low variations among the inverters.

A Unique Solution-Processable n-Type Semiconductor Material Design for High-Performance Organic Field-Effect Transistors

There have been only a limited number of reports on solution-processed n-channel organic thin-film transistor (OTFT) devices with high levels of electrical performance because the material design process for n-type organic semiconductors is relatively difficult compared with p-type semiconductors, and further chemical modification of the functional groups is required. As a result, the development of soluble n-type organic semiconductors with high carrier mobilities has remained a challenge. Our work addresses this by introducing a novel molecular design to realize soluble n-type organic semiconductors with high electron mobilities through the simple substitution of trifluoromethyl or trifluoromethoxy groups at the meta positions to support sufficient solubility, creating suitable LUMO energy levels and high crystallinity. These newly designed benzobis(thiadiazole) (BBT)-based molecules showed electron mobilities as high as 0.61 cm2 V–1 s–1 in solution-processed OTFT devices. As a practical application in printed electronics, we demonstrated an organic complementary inverter circuit with OTFT devices using the developed soluble organic semiconductors. Because of their high solubility level and superior electrical properties compared with common para-substituted derivatives, the utilization of meta substituents is a new strategy for the design of soluble organic semiconductors in the field of OTFT device fabrication.

High-Performance Printed Organic Ambipolar Complementary Inverters with Polyazine Containing Diketopyrrolopyrrole

We report ambipolar organic field effect transistors (OFETs) and complementary inverters based on polyazine containing diketopyrrolopyrrole (PBTDAZ). PDBTAZ OFETs showed well-balanced electron and hole mobilities of 0.13 and 0.12 cm2/(V·s) at a low annealing temperature of 100oC using bottom-contact, top-gate geometry with a CYTOPTM gate dielectric layer. The mobilities were improved to 0.56 cm2/(V·s) by thermal annealing (150°C). The ambipolar complementary-inverter-based PDBTAZ OFETs showed ideal Vinv near half of VDD with a high gain of 15∼20 due the well-balanced electron and hole mobilities.

Micro-scale twistable organic field effect transistors and complementary inverters fabricated by orthogonal photolithography on flexible polyimide substrate

We fabricated micro-scale organic field effect transistors (OFETs) and complementary inverters on a twistable polyimide (PI) substrate by applying orthogonal photolithography. By applying a highly fluorinated photoresist and development solvent, it becomes possible to create organic electronic devices with a micro-scale channel length without damaging the underlying polymer films. The 3μm-channel twistable pentacene OFET devices and complementary inverters created using p-type pentacene and n-type copper hexadecafluorophthalocyanine exhibited stable electrical characteristics from flat to twist configurations (angle of up to ∼50°). The realization of twistable micro-scale OFETs and inverter devices on a PI substrate may enable the production of functioning organic devices in practical, flexible configurations.

High-performance organic complementary inverters using monolayer graphene electrodes.

Chemical vapor deposition-grown graphene has been an attractive electrode material for organic electronic devices, such as organic field-effect transistors (OFETs), because it is highly conductive and provides good oxidation and thermal stability properties. However, it still remains a challenge to demonstrate organic complementary circuits using graphene electrodes because of the relatively poor performance of n-type OFETs. Here, we report the development of high-performance organic complementary inverters using graphene as source/drain electrodes and N, N'-ditridecyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-C13) and pentacene as n- and p-type organic semiconductors, respectively. Graphene electrodes were n-doped via the formation of NH2-terminated self-assembled monolayers that lowered the work function and the electron injection barrier between the graphene and PTCDI-C13. Thermal annealing improved the molecular packing among PTCDI-C13 groups on the graphene surface, thereby increasing the crystallinity and grain size. The thermally annealed PTCDI-C13 OFETs prepared using n-doped graphene electrodes exhibited a good field-effect mobility of up to 0.43 cm2/(V s), which was comparable to the values obtained from other p-type pentacene OFETs. By integrating p- and n-type OFETs, we successfully fabricated organic complementary inverters that exhibited highly symmetric operation with an excellent voltage gain of up to 124 and good noise margin.

The application of orthogonal photolithography to micro-scale organic field effect transistors and complementary inverters on flexible substrate

Micro-scale pentacene organic field effect transistors (OFETs) were fabricated on a flexible poly(ethylene terephthalate) (PET) substrate. By applying a highly fluorinated developing solvents and its compatible photoresist materials, it has become possible to make the micro-scale patterning for organic devices using standard photolithography without damaging the underlying polymer layers. The flexible pentacene OFETs with 3 μm-sized channel length exhibited stable electrical characteristics under bent configurations and under a large number of repetitive bending cycles. Furthermore, we demonstrated micro-scale organic complementary inverters on a flexible PET substrate using p-type pentacene and n-type copper hexadecafluorophthalocyanine materials.

Cellulose as biodegradable high-k dielectric layer in organic complementary inverters

We report on the natural source based and biodegradable material cellulose on Al2O3 as ultrathin hybrid high-k dielectric layer for applications in green electronics. Dielectric films of 16 nm cellulose (ε ≈ 8.4) and 8 nm Al2O3 (ε ≈ 9) exhibit low leakage currents up to electric fields of 1.5 MV/cm. Pentacene and C60 based organic thin film transistors show a well-balanced performance with operation voltages around 2 V. They are implemented in complementary inverters with excellent switching behavior, a small-signal gain up to 60 and with exceptionally high and balanced noise margin values of 82% at ultralow operation voltage (VDD = 2.5 V).

ZrO2 dielectric-based low-voltage organic thin-film inverters

In this paper, the authors first report ZrO2-dielectric based low-voltage organic thin-film complementary metal-oxide semiconductor inverters. Two active layers of p-type pentacene and n-type N,N′-dioctyl-3,4,9,10-perylenedicarboximide were successively deposited on the thermally stable, transparent ZrO2 using the neutral cluster beam deposition method. Based on the good balance between p- and n-type transistors, the complementary inverters exhibited ideal characteristics including sharp inversions, complete switching, high gains, and large voltage swings at low operating voltage levels.

Low-voltage organic complementary inverters fabricated with pentacene/SrTiO3and C60/SrTiO3field-effect transistors

Organic complementary inverters were fabricated with low-voltage pentacene/SrTiO3 and C60/SrTiO3 field-effect transistors (FETs), without formation of self-assembled monolayer on surface of the dielectric SrTiO3. The inverters showed the highest gain of 18.4 at an operating voltage as low as 3 V, where the pentacene/SrTiO3 and C60/SrTiO3 FETs on the inverters showed hole and electron mobilities of 0.85 and 0.07 cm2/V s with threshold voltages (VT) of −1.1 and −0.2 V, respectively.

High performance CMOS-like inverter based on an ambipolar organic semiconductor and low cost metals

We report the fabrication of simply structured and high performance organic complementary inverters based on an ambipolar organic semiconductor, 8,9,10,11-tetrachloro-6,13-bis-(triisopropylsilylethynyl)-1-azapentacene (4Cl-Azapen). Individual transistors using symmetric Au electrodes showed high and balanced performance, with good hole (up to 0.23 cm2V−1s−1) and electron (up to 0.21 cm2V−1s−1) mobilities. Integrated complementary inverters showed sharp inversions with high gains (>180) and negligible hysteresis. The inverters using low-cost electrodes, Ag and Cu, also exhibited high gains and high noise margins (>75% of the ideal value).

Spray-printed organic field-effect transistors and complementary inverters

We report the fabrication of high-performance organic field-effect transistors (OFETs) and complementary inverters using spray-printed films of n-type small-molecule semiconductors and p-type conjugated polymers. Highly crystalline organic semiconductor films could be obtained by controlling the droplet size, nozzle-to-substrate distance, and solvent drying speed during the printing process. After the optimisation of the spray-printing process, the performances of the spray-printed OFETs were comparable to those of spin-coated and inkjet-printed OFETs. In addition to excellent device-to-device uniformity, the spray-printed n- and p-channel OFETs also exhibited high field-effect mobilities, which were ∼0.3 (ActivInk™ N1450, Polyera), ∼0.01 (regioregular-poly(3-hexylthiophene) (rr-P3HT)), and ∼0.25 cm2 V−1 s−1 (ActivInk™ P2100, Polyera). Organic complementary inverters were fabricated by spray printing and shadow-mask patterning while using ActivInk™ N1450 and P2100 as the n- and p-type semiconductors, respectively. The complementary inverters exhibited a large voltage gain (∼17) and a low power consumption (∼0.02 mW) at VDD = 60 V.

π-Conjugated organic-based devices with different layered structures produced by the neutral cluster beam deposition method and operating conduction mechanism

The authors report on the systematic characterization of structural effects of organic complementary inverters based on two π-conjugated organic molecules, pentacene and copper hexadecafluorophthalocyanine (F16CuPc). Three classes of inverters with different layered structures in top-contact configuration were produced using the neutral cluster beam deposition method. Their voltage transfer characteristics, gain curves and hysteresis behaviour were characterized with respect to their thickness. Class I inverters, with generic structures of single-layered, p-and n-type (200/180 Å) transistors, exhibited high gains of 12.8 ± 1.0 with sharp inversions. Their two constituent transistors, with hole and electron mobilities of 0.38 cm2 V−1 s−1 and 7.0 × 10−3 cm2 V−1 s−1, respectively, showed well-coupled carrier conduction during operation. The behaviour of class II and III inverters, with layered heterojunction structures, was independent of upper-layer thickness and did not show hysteresis. The better performances of class II inverters, which showed high gains of 14.4 ± 1.1, were rationalized partly in terms of decreased mobility differences between their constituent transistors. Heterojunction geometries can be applied to obtain high-performance, fast-switching inverters by avoiding direct exposure of the air-sensitive transistors to ambient conditions. The inverters' general operating conduction mechanism is also discussed.

Device characteristics of perylene-based transistors and inverters prepared with hydroxyl-free polymer-modified gate dielectrics and thermal post-treatment

Organic field-effect transistors (OFETs) and complementary inverters were produced on the basis of n-type N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) using the neutral cluster beam deposition (NCBD) method. Significant improvements in surface morphology and crystallinity were observed after the surface modification of SiO2 gate dielectric layers with hydroxyl-free polymer insulators such as polymethylmethacrylate (PMMA) and cyclic olefin copolymer (COC), and thermal post-treatment. Electric characteristics and operational stability of PTCDI-C8-based OFETs were also clearly enhanced after the surface modification, and in particular, the thermally post-treated OFETs with COC-modified SiO2 gate dielectrics exhibited a high room-temperature mobility of 0.68cm2/Vs. Two structural types (generic vs. encapsulated) of inverters in top-contact configuration were fabricated by integration of the p-type pentacene and n-type PTCDI-C8 OFETs using COC-modified SiO2 gate dielectrics. Due to the increased electron mobilities and good coupling between p- and n-type OFETs, hysteresis-free, fast-switching inverters were realized with high gains of ∼20 in the first and third quadrants of voltage transfer characteristics under ambient conditions. The device characteristics of the encapsulated inverters monitored as a function of the time were well maintained with slight degradation.