Organic Single-crystal Transistors Research Articles

Ambipolar light-emitting organic single-crystal transistors with a grating resonator.

Electrically driven organic lasers are among the best lasing devices due to their rich variety of emission colors as well as other advantages, including printability, flexibility, and stretchability. However, electrically driven lasing in organic materials has not yet been demonstrated because of serious luminescent efficiency roll-off under high current density. Recently, we found that the organic ambipolar single-crystal transistor is an excellent candidate for lasing devices because it exhibits less efficient roll-off, high current density, and high luminescent efficiency. Although a single-mode resonator combined with light-emitting transistors (LETs) is necessary for electrically driven lasing devices, the fragility of organic crystals has strictly limited the fabrication of resonators, and LETs with optical cavities have never been fabricated until now. To achieve this goal, we improved the soft ultraviolet-nanoimprint lithography method and demonstrated electroluminescence from a single-crystal LET with a grating resonator, which is a crucial milestone for future organic lasers.

Band-like transport down to 20 K in organic single-crystal transistors based on dioctylbenzothienobenzothiophene

Band-like transport has been realized down to 20 K in solution-processed single-crystal transistors based on dioctylbenzothienobenzothiophene. The mobility increases from 16 to 52 cm2/V s as the temperature is lowered from 300 to 80 K. An abrupt mobility drop is observed around 80 K, but even below 80 K, gradually increasing mobility is restored again down to 20 K instead of thermally activated transport. From the observation of a shoulder structure in the transfer curve, the mobility drop is attributed to a discrete trap state.

All solution-processed organic single-crystal transistors with high mobility and low-voltage operation

High-mobility organic single-crystal field-effect transistors of 3,11-didecyldinaphtho[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]-dithiophene (C10-DNBDT) operating at low driving voltage are fabricated by an all-solution process. A field-effect mobility as high as 6.9cm2/Vs is achieved at a driving voltage below 5V, a voltage as low as in battery-operated devices, for example. A low density of trap states is realized at the surface of the solution-processed organic single-crystal films, so that the typical subthreshold swing is less than 0.4V/decade even on a reasonably thick amorphous polymer gate dielectrics with reliable insulation. The high carrier mobility and low interface trap density at the surface of the C10-DNBDT crystals are both responsible for the development of the high-performance all-solution processed transistors.

Retraction: Organic Single-Crystal Transistors with Secondary Gates on Source and Drain Electrodes [e-J. Surf. Sci. Nanotech. Vol. 6, pp. 138-141 (2008)

Retraction: Organic Single-Crystal Transistors with Secondary Gates on Source and Drain Electrodes [e-J. Surf. Sci. Nanotech. Vol. 6, pp. 138-141 (2008)

Single-displacement controlled spontaneous electrolysis towards CuTCNQ microribbon electrodes in organic single-crystal transistors.

Using single-displacement controlled spontaneous electrolysis solution-prepared CuTCNQ microribbons as the source/drain electrodes, we have fabricated 9,10-bis(2-phenylethynyl)anthracene (BEPA) based organic single crystal top-contact field-effect transistors. The interfacial energetic match between organic semiconductors and CuTCNQ electrodes with the low contact resistance accounts for the compelling improvement in electrical characteristics relative to the copper electrode, even comparable to gold counterparts. Furthermore, we have estimated the contact resistance of single-crystal transistors by the transfer line method (TLM).

Effect of grain boundary on the field-effect mobility of microrod single crystal organic transistors.

High-performance microrod single crystal organic transistors based on a p-type 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor are fabricated and the effects of grain boundaries on the carrier transport have been investigated. The spin-coating of C8-BTBT and subsequent solvent vapor annealing process enabled the formation of organic single crystals with high aspect ratio in the range of 10 - 20. It was found that the organic field-effect transistors (OFETs) based on these single crystals yield a field-effect mobility and an on/off current ratio of 8.04 cm2/Vs and > 10(5), respectively. However, single crystal OFETs with a kink, in which two single crystals are fused together, exhibited a noticeable drop of field-effect mobility, and we claim that this phenomenon results from the carrier scattering at the grain boundary.

Solution-processed high-performance flexible 9, 10-bis(phenylethynyl)anthracene organic single-crystal transistor and ring oscillator

Organic semiconductor of 9, 10-bis(phenylethynyl)anthracene (BPEA) single crystal ribbon with ultra-long length has been prepared by solution drop casting method, where the growth direction was controlled with the seed crystal. The BPEA single crystal ribbon based field-effect transistors show high hole mobility up to 3.2 cm2/V·s, and the inverters exhibited the highest gain of 92. The complex device such as 5-stage ring oscillator consisting of 10 transistors was also constructed on a single crystal ribbon. This straightforward methodology was applied to fabricate plastic transistors on the flexible substrate, showing high performance even after repeatedly bending of 300 times.

High performance, air stable n-type single crystal transistors based on core-tetrachlorinated perylene diimides.

Organic single crystal transistors based on two kinds of core-tetrachlorinated perylene diimides (4ClPDIs) are fabricated. Compared with alkyl substituted 4ClPDI, the transistors based on fluoroalkyl substituted 4ClPDI exhibit an air-stable electron mobility of up to 1.43 cm(2) V(-1) s(-1) and high photocurrent with an on/off ratio of 1000, which are associated with its close packing arrangement.

Self-assembly, Physicochemical, and Field-effect Transistor Properties of Solution-crystallized Organic Semiconductors Based on π-Extended Dithieno[3,2-b:2′,3′-d]thiophenes

Abstract Thienoacene-based π-conjugated oligomers, DTT-NP8 and DTT-BT8, were designed and synthesized. Their strong intermolecular interactions originating from S···S contacts enable the fabrication of single-crystal microribbons via solution processing. Organic single-crystal transistors exhibited field-effect mobilities as high as 0.54 cm2 V−1 s−1 and on/off current ratio of ca. 106.

Multi-color light-emitting transistors composed of organic single crystals

We report a novel concept for multi-color light emission from an ambipolar organic single-crystal transistor using natural optical waveguides, the self-absorption effect, Davydov splitting and the unique alignment of the transition dipole moments. We used 9,10-bis-(2,2-diphenylvinyl)-anthracene single crystals to produce blue and green light from identical single-crystal transistors. We also observed red light, which corresponds to the emission from in-gap states that are caused by impurities. Importantly, each of these different colors corresponds to a distinguishable light polarization, which enables us to tune the emission color by using a light polarizer.

High-speed organic single-crystal transistors gated with short-channel air gaps: Efficient hole and electron injection in organic semiconductor crystals

Short-channel, high-mobility organic filed-effect transistors (OFETs) are developed based on single crystals gated with short-channel air gaps. The high hole mobility of 10cm2/Vs for rubrene, and high electron mobility of 4cm2/Vs for PDIF-CN2 crystals are demonstrated even with a short channel length of 6μm. Such performance is due to low contact resistance in these devices estimated to be as low as ∼0.5kΩ cm at gate voltage of −4V for rubrene. With the benefit of the short channel length of 4.5μm in a new device architecture with less parasitic capacitance, the cutoff frequency of the rubrene air–gap device was estimated to be as high as 25MHz for drain voltage of −15V, which is the fastest reported for p-type OFETs, operating in ambient conditions.

Electrolyte gated single-crystal organic transistors to examine transport in the high carrier density regime

Abstract

Strategies for Fabricating Nanogap Single-Crystal Organic Transistors

Nanotechnology is an emerging technology for fabricating nanostructures where at least one dimension is smaller than 100 nm. This paper explains how single-crystal organic transistors of channel length down to just 7 nm can be fabricated without damaging the organic material. Single crystals of C60, rubrene, and pentacene have been chosen in our structures, but the same process can be used for a wide variety of organics. The method combines high-resolution electron-beam lithography and vacuum device assembly with piezo manipulators. As modern devices are typically designed with short semiconducting channel length, this type of fabrication methods allows downscaling of organic electronic devices for research purposes.

High-speed solution-processed organic single crystal transistors using a novel triisopropylsilylethynyl anthracene derivative

A high-quality organic single crystal transistor (OSCT) was fabricated via solution-processing using a novel anthracene derivative (TIPsAntNE). The OSCT fabricated on a surface-modified high-capacitance ZrOx substrate provided a transistor that operated at low voltages with a high mobility up to 4.1 cm2/Vs and negligible hysteresis (a Vth shift of <20 mV). Importantly, the TIPsAntNE OSCT functioned under a high-frequency AC signal with a gate bias as high as 30 kHz. These are crucial operational requirements for commercial applications of organic transistors. The photoresponsivity (>1 A/W) of the TIPsAntNE single crystal was high over a wide range across the visible spectrum.

Surface Selectively Deposited Organic Single-crystal Transistor Arrays with High Device Performance

A method for patterning organic single-crystal transistor arrays via surface selective deposition is presented. Solvent-vapor annealing is applied for the formation of organic crystals under ambient conditions. The devices are fabricated with a dual-gate structure, which allows the investigation of device performances of bottom-gate/top-contact (BG/TC) and top-gate/top-contact (TG/TC) structures based on the same crystals. The resulting BG/TC devices exhibit the field-effect mobility (μFET) up to 3.5 cm2/Vs. And μ FET is influenced by the contact resistance, resulting in large variation in device performance. On the other hand, TG/TC structure exhibits better performance with smaller variation. The highest μ FET is 7.4 cm2/Vs.

Copper-Catalyzed Tandem Synthesis of Indolo-, Pyrrolo[2,1-a]isoquinolines, Naphthyridines and Bisindolo/Pyrrolo[2,1-a]isoquinolines via Hydroamination of ortho-Haloarylalkynes Followed by C-2 Arylation

An efficient approach for the copper-catalyzed regioselective tandem synthesis of diversely substituted indolo[2,1-a]isoquinolines 11a-r, pyrrolo[2,1-a]isoquinolines 12a-d, and indolo-, pyrrolo[2,1-f][1,6]naphthyridines 14a-f via preferential addition of the heterocyclic amines onto the ortho-haloarylalkynes over N-arylation followed by intramolecular C-2 arylation is described. The scope of the developed chemistry was successfully extended for the direct synthesis of bisindolo-, pyrrolo[2,1-a]isoquinolines 15a-g, a regioisomer of the bisindolo[1,2-a]quinolines used as organic single-crystal field-effect transistor. Hydroxymethyl benzotriazole, which is an inexpensive and air stable compound, has been used as a ligand to carry out this one-step conversion of simple, readily available starting materials into an interesting class of heterocyclic compounds.

Organic single crystal transistor characteristics of single-crystal phase pentacene grown by ionic liquid-assisted vacuum deposition

Organic transistor characteristics of single-crystal phase pentacene were investigated. Ionic liquids (ILs) were used as not only a gate dielectric material in the transistors but also a crystallization solvent in vacuum deposition of pentacene. The crystal sizes reached 200 μm and their surface exhibits a molecularly step-and-terrace structure. There was no sign of IL molecules inside the crystal, and the impurity level of 6,13-pentacenequinone was also reduced. The average value of the field-effect mobility was not so inferior to those for the conventional pentacene single crystals, and the highest value exceeded 5 cm2/Vs, with the on/off current ratio of 104.

High Mobility, Air Stable, Organic Single Crystal Transistors of an n‐Type Diperylene Bisimide

Recently, some impressive progress has been made by functionalization of (hetero-)acenes, thiophenes, and arylenes with electron-defi cient constituents. [ 3–5 ] However, the development of air-stable, high mobility, n-type organic semiconductors for organic electronics is still highly emergent. The mobility of organic semiconductors depends on the effi ciency of charge transport from one molecule to another. Hence, some organic semiconductors with dense molecule packing always give high mobility. [ 6 ] As to the stability of organic compounds, it is believed that the highest occupied molecular orbital (HOMO) of p-type organic semiconductors should be more negative than –5.0 eV, e.g., locating at –5.0 to –6.0 eV, and the lowest unoccupied molecular orbitals (LUMO) of n-type organic semiconductors are best located between –4.0 and –4.5 eV, for anti-oxidation in air. [ 2 , 7 ] We have acknowledged these requirements and believe that perylene bisimides (PBIs) will fi t as candidates because of their reasonable electron acceptor ability, [ 8 ] and have been focusing on the expansion of the chemistry of perylene bisimides (PBIs) by a combination of Ullmann coupling and C–H transformation for some time, and have developed a facile strategy to synthesize fully conjugated, triply linked, diperylene bisimides, [ 8 ] conferring the expanded

High performance n-type single crystalline transistors of naphthalene bis(dicarboximide) and their anisotropic transport in crystals

High-performance n-type organic single crystal transistors of a naphthalene diimide are demonstrated. The accomplished transistors exhibit electron mobility as high as 0.7 cm(2) V(-1) s(-1). The anisotropic charge transport in the elongated hexagonal crystals of the naphthalene diimide is also explored. The transport anisotropy along different directions is at least 1.6 (mobility ratio).

Short-channel and high-mobility p- and n-type organic single-crystal transistors with air-gap structures

ABSTRACTIn an effort to realize high-speed organic logic components, p- and n-type single-crystal organic field-effect transistors (SC-OFETs) were fabricated using air-gap structures with channel lengths as short as several μm. High carrier mobility of about 10 cm2/Vs is demonstrated in rubrene SC-OFETs even with the short channel length of 6 μm, using Si-based microstructures. The contact resistance is estimated to be 450 Ohm cm, which is only 5% of the total channel resistance between source and drain electrodes. Performances of n-type air-gap devices based on PDIF-CN2 are also demonstrated exhibiting electron transport with the carrier mobility of about 2 cm2/Vs. Furthermore, micron-scale air-gap structures are fabricated using insulating materials on glass substrates to reduce parasitic gate capacitance. The cut-off frequency of this rubrene air-gap device is measured to be as high as 8 MHz with applied drain voltage VD of 15 V. These techniques are promising to be applicable to next-generation organic high-speed logic circuits.