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Organic semiconductors make them interesting candidates for the development of innovative and disruptive applications also in large area and flexible sensor devices. In fact, organic-based photoactive media combine effective light absorption in the region of the spectrum from ultraviolet to near-infrared with good photogeneration yield and low-temperature processability over large areas and on any substrate. Moreover, their electronic properties can be easily tuned to optimize, charges transport depending on the targeted application in the field of imaging, tactile or biomedical sensing. We made curved surface sensor array by thermal molding of planer device array on thin plastic film.

Organic sensor array were fabricated on a curved plastic substrate of which Gauss curvature was finite. In this work, we proposed soft robot finger as one of the test case of curved surface device, that have artificial tactile sense by detecting slight deformation induced by touching an object. We made curved surface sensor array by thermal molding of organic thin film transistors fabricated on thin plastic film. Because both organic thin film and thin plastic substrate film are sufficiently soft and flexible, we successfully detected the strain distribution which is induced by a slight deformation. Observed data indicate that the induced strain is classified into the tensile and compressive strain depending on the pixel location, and corresponds to the amount of Ah, and in addition, real time detection is achieved. We expect this ‘electronic artificial tactile sense’ will be connected with the recent AI technologies, and sensitive robot finger in the precision work field will be realized in the near future.

[Abstract] Carrier-injection and the succeeding pre-channel-formation dynamics in organic thin-film transistor was observed using time-domain reflectometry. Having previously analyzed the depth-wise variation in the initial carrier-injection from the contact electrode to the channel region, we focus here on the succeeding pre-channel-formation dynamics. We demonstrate that a hole concentration in the semiconductor/gate insulator interface increases until its electrical capacitance is filled through contact and access resistances. Thereafter, the injected-hole dis-tribution gradually spreads. A reduction in both contact and access resistances is crucial not only for the static characteristics of the field effect transistor but also the dynamical response.

[Abstract] Organic sensor array was fabricated on a curved plastic film substrate of which Gauss curvature was finite. In this work, we proposed soft robot finger as one of the test cases of curved surface device that has artificial tactile sense by detecting slight deformation induced by touching an object. We made curved surface sensor array by thermal molding of planer device array on thin plastic film. Observed electrical current in each sensor pixel reflected strain distribution and time response induced by external slight displacement applied.

We propose time-domain reflectometry as an effective tool to investigate the dynamics of electronic devices. We use this technique to experimentally detect with 10 ns time resolution the dynamic process of carrier injection from the contact electrode into an organic thin film transistor as a time evolution of the device impedance. This method allows us to trace vertical carrier injection in the thickness direction.

Innovative sensing systems based on THz electromagnetic waves have been attracting a great deal of attention. Although many THz detectors have been developed over the years, it is currently difficult to manufacture low-cost THz sensing/imaging devices. In the present study, we propose to use organic field-effect transistors (OFETs) and small potential fluctuation against the carriers within them (N. Ohashi, H. Tomii, R. Matsubara, M. Sakai, K. Kudo, M. Nakamura, Appl. Phys. Lett. 91 (2007) 162105). We use THz time-domain spectroscopy for OFETs in which the carrier density in the pentacene active layer is modulated by the gate bias. We found evidence that the accumulated free holes in pentacene films can be excited by THz photons to overcome the surrounding barriers in the fluctuating potential. The Drude–Lorentz model could not account for the shape of the absorption spectra, which suggests that the holes are weakly restricted by the potential fluctuation. The integrated absorption intensity was proportional to the transfer characteristics of the OFETs. The present findings represent an important step toward developing a new class of THz-wave sensors.

The usual silicon-based display back planes require fairly high process temperature and thus the development of a low temperature process is needed on flexible plastic substrates. A new type of flexible organic light emitting transistor (OLET) had been proposed and investigated in the previous work. By using ultraviolet/ozone (UV/O3) assisted thermal treatments on wet processed zinc oxide field effect transistor (ZnO-FET), through low-process temperature, ZnO-FETs were fabricated which succeeded to achieve target drain current value and mobility. In this study, physical property evaluation of ZnO was conducted in term of their crystallinity, the increase composition of ZnO formed inside the thin film and the decrease of the carbon impurities originated from aqueous solution of the ZnO itself. The X-ray diffraction (XRD) evaluation showed UV/O3 assisted thermal treatment has no obvious effect towards crystallinity of ZnO in the range of low process temperature. Moreover, through X-ray photoelectron spectroscopy (XPS) evaluation and Fourier transform infrared (FT-IR) spectroscopy evaluation, more carbon impurities disappeared from the ZnO thin film and the increase of composition amount of ZnO, when the thin film was subjected to UV/O3 assisted thermal treatment. Therefore, UV/O3 assisted thermal treatment contributed in carbon impurities elimination and accelerate ZnO formation in ZnO thin film, which led to the improvement in the electrical property of ZnO-FET in the low-process temperature.

We controlled the in-plane orientation of pentacene grains by graphoepitaxy using patterned amorphous-SiO2/Si substrates on which periodic grooves with slope edges had been formed. Pentacene crystals exhibited a clear tendency to align their b-axes perpendicular to the groove edges. Organic thin-film transistors were fabricated on the patterned and flat substrates and their transistor characteristics were compared. Although the patterned substrates increased the apparent mobility by only 10–20%, the number of grain boundaries with high potential barriers to carrier transport was reduced to half of that on flat substrates. This improvement is expected to enhance the response speed of pentacene organic thin-film transistors and suppress the sensitivity of their characteristics to the operating temperature.

We have demonstrated the inverter operation of stacked-structure CMOS devices using pentacene and ZnO as active layers. The fabrication process of the device is as follows: A top-gate-type ZnO thin-film transistor (TFT), working as an n-channel transistor, was formed on a glass substrate. Then, a bottom-gate-type pentacene TFT, as a p-channel transistor, was fabricated on top of the ZnO TFT while sharing a common gate electrode. For both TFTs, solution-processed silicone-resin layers were used as gate dielectrics. The stacked-structure CMOS has several advantages, for example, easy patterning of active material, compact device area per stage and short interconnection length, as compared with the planar configuration in a conventional CMOS circuit.

Organic static induction transistors, which have relatively short vertical channels, are attractive devices for their low operating voltage and high operating speed. However, a gate voltage larger than the Schottky barrier potential usually leads to a large gate leakage current and thus poor device performance. To limit the gate leakage current, we considered adding insulating layers around the gate electrode. The oxidization of aluminum during a physical vapor deposition process was used to form insulating layers around the gate electrode. The results demonstrate that by appending gate insulating layers, gate leakage currents can be effectively reduced and device characteristics, especially the on/off ratio, can be improved.

Extrinsic factors to disturb the carrier transport in pentacene field-effect transistors (FETs), as a representative of the high-mobility organic FETs (OFETs), have been comprehensively analyzed by using atomic-force-microscope potentiometry (AFMP), microscopic four-point-probe field-effect transistor (MFPP-FET) measurement, and other techniques. In the first part, by mainly using AFMP as a powerful tool to reveal the potential distribution in working OFETs, we show how and how much the formation of source/drain electrodes influences the apparent field-effect mobility both for top- and bottom-contact configurations. In the second part, we show the influence of irregular grain structures and regular grain boundaries. The films grown both at very low and high temperature ranges contain distinctive insulating parts, which make the apparent mobility very low. Within the moderate growth temperature range, the intrinsic field-effect mobility obtained by MFPP-FET measurement is proportional to the average grain size. This behavior is well explained by the polycrystalline model with the diffusion theory. According to the observations in this work, it is obvious that these extrinsic limiting factors must be carefully excluded to discuss the intrinsic mechanism of the carrier transport in OFETs.

Organic static induction transistor (OSIT) is a promising driving device for the displays, since it shows high-speed, high-power and low-voltage operation. In this study, the OSIT with fine gate electrode patterned by electron beam exposure were fabricated. We investigated the basic electrical characteristics of copper phthalocyanine OSIT and compared with the calculation results obtained by two-dimensional (2D) device simulator. The experimental results show that the gate modulation improved by reducing the electrode gap and on/off current ratio depends on the gate gap.

The control of the organic field-effect transistor characteristics is necessary to produce the integrated circuits using organic semiconductors. Variations in the poly (3-hexylthiophene) field-effect transistor characteristics upon post-treatment such as thermal treatment and voltage treatment in N 2 atmosphere have been investigated. The controllability and reproducibility of the threshold voltage and mobility were achieved as a result of the post-treatments.

We fabricated both thin film transistors (TFTs) and diodes using zinc oxide (ZnO) and pentacene, and investigated their basic characteristics. We found that field-effect mobility is influenced by the interface state between the semiconductor and dielectric layers. Furthermore, the complementary metal oxide semiconductor (CMOS) inverter using a p-channel pentacene field-effect transistor (FET) and an n-channel ZnO FET showed a relatively high voltage gain (8 - 12) by optimizing the device structure. The hybrid complementary inverters described here are expected for application in flexible displays, radio frequency identification cards (RFID) tags, and others.

By exploiting atomic-force-microscope potentiometry, we have studied the local potential distribution in the solutionprocessible tetrabenzoporphyrin (BP) bottom-contact thin-film transistor under controlled atmospheres. It is found that abrupt and big potential drops mainly appeared at the domain boundaries and cracks in the BP film when the transistor was under operation, indicating a dominant influence of domain boundary and crack on the device performance. Exposure of the device to O2 drastically reduced the potential drops at some boundaries, which is the main reason for the improved device performance by O2 exposure. 2008 Elsevier B.V. All rights reserved.

We report two types of integrated circuits based on a pentacene static-induction transistor (SIT), a pentacene thin-film transistor (TFT) and a zinc oxide (ZnO) TFT. The operating characteristics of a p-p inverter using pentacene SITs and a complementary inverter using a p-channel pentacene TFT and an n-channel ZnO TFT are described. The basic operation of logic circuits at a low voltage was achieved for the first time using the pentacene SIT inverter and complementary circuits with hybrid inorganic and organic materials. Furthermore, we describe the electrical properties of the ZnO films depending on sputtering conditions, and the complementary circuits using ZnO and pentacene TFTs.

For the realization of high-performance organic static induction transistors (OSITs), it is important to investigate the effect of a hole injection barrier at the interface between a pentacene films and a source electrode in OSITs. In this study, the OSITs based on pentacene films were fabricated on various metallic source electrodes with different work functions and on copper phthalocyanine (CuPc)/indium tin oxide (ITO) electrodes with different CuPc thicknesses. The hole injection barrier was affected by the work function of metallic source electrodes (ITO, Au, and Pt) and the thickness of CuPc (0, 3, and 5 nm). The obtained results demonstrate that a high on/off ratio is achieved when a hole injection barrier with a moderate height is formed at the interface. It was found that controlling the hole injection barrier is effective for improving the characteristics of OSITs.

Organic light-emitting diodes (OLEDs) combined with thin film transistor (TFT) are well suitable elements for low-cost, large-area active matrix displays. On the other hand, zinc oxide (ZnO) is a transparent material and its electrical conductivity is controlled from conductive to insulating by growth conditions. The drain current of ZnO FET is 180 µA. The OLED uses ZnO thin film (Al-doped) for the electron injection layer and is controlled by radio frequency (rf) and direct current (dc) sputtering conditions, such as Al concentration and gas pressure. Al concentration in the ZnO film and deposition rate have strong effects on electron injection. Furthermore, the OLED driven by ZnO FET shows a luminance of 13 cd/m2, a luminance efficiency of 0.7 cd/A, and an on-off ratio of 650.

Organic transistors have attracted considerable interest because they are lightweight, flexible, inexpensive, and highly efficient over large areas. As a result of these characteristics, organic transistors are expected to find use in a variety of applications, including electronic barcodes, displays, and sensors. Until now, their performance has been inferior to inorganic transistors because of their lower mobility values (typical mobility ranges are 1–10 and 500–10 000 cm Vs for organic and inorganic semiconductors, respectively). Attempts to enhance the performance of organic transistors have relied on decreasing the length and increasing the cross-sectional area through which the charge carriers travel. In the case of an organic thin-film transistor (OTFT), which is the most popular type of organic transistor (Fig. 1a), it is necessary to decrease the channel length and increase the channel width by fine patterning the source and drain electrodes. Nanometer-scale devices can be fabricated if state-of-the-art lithographic techniques are used prior to organic-film growth. However, this type of process is not practical for fabricating low-cost, largescale flexible electronics. One approach to resolving this issue is to employ a verticaltype transistor (Fig. 1b). The carrier pathway in a verticaltype transistor is perpendicular to the substrate, and the current is dispersed over a wide area in the device. A static induction transistor (SIT), which is frequently referred to as a solidstate triode, is one of the simplest vertical-type transistors. SITs were first developed using inorganic semiconductors

Organic thin-film transistors (OTFTs) are emerging as aninexpensive alternative to amorphous silicon devices becauseof their many attractive features, such as a simple fabricationprocess, low cost, and mechanical flexibility. Recently, the per-formance of OTFTs has been significantly improved by modi-fying the dielectric surface and/or source and drain (S/D) elec-trodes

For the better performance of organic thin-film transistors (TFTs), gate-insulator surface treatments are often applied. However, the origin of mobility increase has not been well understood because mobility-limiting factors have not been compared quantitatively. In this work, we clarify the influence of gate-insulator surface treatments in pentacene thin-film transistors on the limiting factors of mobility, i.e., size of crystal-growth domain, crystallite size, HOMO-band-edge fluctuation, and carrier transport barrier at domain boundary. We quantitatively investigated these factors for pentacene TFTs with bare, hexamethyldisilazane-treated, and polyimide-coated SiO2 layers as gate dielectrics. By applying these surface treatments, size of crystal-growth domain increases but both crystallite size and HOMO-band-edge fluctuation remain unchanged. Analyzing the experimental results, we also show that the barrier height at the boundary between crystal-growth domains is not sensitive to the treatments. The res...

A well-defined test structure of organic static-induction transistor (SIT) having regularly sized nano-apertures in the gate electrode has been fabricated by colloidal lithography using 130-nm-diameter polystyrene spheres as shadow masks during vacuum deposition. Transistor characteristics of individual nano-apertures, namely 'nano-SIT,' have been measured using a conductive atomic-force-microscope (AFM) probe as a movable source electrode. Position of the source electrode is found to be more important to increase current on/off ratio than the distance between source and gate electrodes. Experimentally obtained maximum on/off ratio was 710 (at V DS = -4V, V GS = 0 and 2V) when a source electrode was fixed at the edge of gate aperture. The characteristics have been then analyzed using semiconductor device simulation by employing a strongly non-linear carrier mobility model in the CuPc layer. From device simulation, source current is found to be modulated not only by a saddle point potential in the gate aperture area but also by a pinch-off effect near the source electrode. According to the obtained results, a modified structure of organic SIT and an adequate acceptor concentration is proposed. On/off ratio of the modified organic SIT is expected to be ∼100 times larger than that of a conventional one.

Static induction transistors (SITs) based on copper phthalocyanine (CuPc) were prepared and the dependence of static and transient characteristics on the edge features of the patterned Al gate electrode was studied. Devices having Al gate electrodes deposited with and without a gap between a shadow mask and the substrate were prepared. Devices prepared in the presence of the gap produces a thin transparent edge for the Al gate electrode which enhances the modulation of the drain current by the gate voltage. However, a repetitive slow transient of the drain current was observed for the devices using gap. This transient is considered to be due to the charge carrier trapping at Al dots in the active channel region.

Conventional organic static induction transistors (OSITs) have been directly fabricated on a source electrode formed on a substrate without the investigation of the effect of a surface treatment on device characteristics. We have fabricated the OSITs based on pentacene thin film with an ultrathin copper phthalocyanine (CuPc) layer. The influence of depositing this ultrathin CuPc layer on the source electrode on static characteristics was investigated. The obtained results provided an important fact indicating that a high on/off ratio of 230 and a high current of 3 µA in an organic SIT are achieved by the formation of a hole injection barrier that works as a tunneling layer on a source electrode. The barrier effectively controls the tunnel current from the source electrode by applying a gate voltage.

We propose a double heterojunction organic light-emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m2 at 22 V and 7.6 mA/cm2. The results obtained here demonstrate that the vertical organic light-emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20151

Organic light emitting transistors which are vertically combined with the organic static induction transistor and organic light emitting diode are fabricated and the device characteristics depending on the structure of gate electrode are investigated. By optimizing the layer thickness and the size of slit-type Al gate electrode, high luminance modulation by low gate voltage as high as 1 V are obtained. The organic light emitting transistor described here is a suitable element for flexible sheet displays.

Organic static induction transistors (SITs) were fabricated with a Au(source)/organic/patterned-Al(gate)/organic/patternedAu(drain) structure employing a new concept, ‘spontaneous patterning of higher order structures’ (SPHOS). A selective mechanical exfoliation process was developed to replicate the pattern of gate electrode after a pre-patterned drain electrode. The I–V curve measured between the gate and the drain electrodes exhibited a good Schottky characteristic and the drain current of the SIT with higher order structure showed a clear modulation by the gate voltage.

We propose a double heterojunction type organic light emitting diodes (OLED) using zinc oxide (ZnO) films, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of novel OLED were obtained as high as 470cd/m2at 22V and 7.6mA/cm2. The results obtained here demonstrate that the vertical type organic light emitting transistor (OLET) using ZnO layer as an electron injection layer is expected as a key element for flexible sheet displays.

Organic semiconductor transistors are expected for flexible displays, information tags, and the like. However, organic transistors have some disadvantages of current density and speed of operation, because of their high resistivity and low carrier mobility. To improve their performance, it is valuable to analyze the mechanism of operation. We have compared characteristics of lateral- and vertical-type transistors using pentacene evaporated films. The pentacene lateral-type FET characteristics showed large variation due to fabrication parameters such as deposition rate, substrate temperature, and film thickness. It was found that evaporated pentacene thin films have large grain gaps, which disturb carrier flow along the channel formed pentacene film/SiO2 interface direction and make FET characteristics unstable. It is assumed that pentacene films are not suitable lateral-type transistors. Accordingly, we have fabricated vertical-type organic static induction transistors (SITs) using pentacene evaporated films. The pentacene SITs show high-speed operation (cutoff frequency of 7.5 kHz) at relatively low voltages. Further optimization of SIT structure will improve the device performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 43–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10500

We have fabricated organic light emitting transistors (OLET) combining static induction transistor with organic light emitting diode and investigated static and dynamic characteristics. The luminance of OLET is controlled by gate voltages as low as 1 V and excellent dynamic operation is obtained at 60 Hz. The results obtained here show that the OLET is a suitable element for flexible sheet displays.

We have fabricated tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) molecular wires between a parallel cathode and anode (100 µm electrode gap) using the co-evaporation technique with an applied electric field. Wire-shaped microcrystals of TTF-TCNQ grew along the electric field. We have succeeded in fabricating connected wires with an optimum applied voltage. A narrow-gap (20 µm) electrode was used to grow wires with a low applied voltage, which make it possible to fabricate the connected wires easily. The measured I-V curve indicated Ohmic contact between the gold electrode and TTF-TCNQ. Semiconductor-like conduction of the fabricated TTF-TCNQ sample was shown by the temperature dependence of conductivity. Some of the co-evaporated TTF-TCNQ wires may tend to be semiconducting due to nonstoichiometry of TTF1-δ-TCNQ1.

Vertical type field effect transistors (FETs) are expected to be used for various organic devices because of their low-voltage, high-current and high-speed operation. We have fabricated lateral and vertical type FETs using copper-phthalocyanine evaporated films and measured the basic static and dynamic characteristics of these FETs. Although both transistors show field effect characteristics, the vertical type FET showed high-frequency and high-current characteristics under relatively low-voltage conditions as compared with those of lateral type FETs. These results demonstrate that the vertical FET operates as a static induction transistor and the short length between the source, drain and gate electrodes in the device structure improves the device characteristics.

We have fabricated field-effect transistors (FETs) using a TMTSF (donor) and TCNQ (acceptor) layered structure and investigated the basic FET characteristics. The transconductances of FETs depended on the substrate temperature.

Organic static induction transistors (SITs) for display devices are proposed and the basic electrical characteristics of the SITs are investigated. The organic SITs, using a copper phthalocyanine (CuPc) evaporated film as an active layer, have a layered structure of Au (drain)/CuPc/Al (gate)/CuPc/Au (source)/glass. The electrical characteristics show that the current flow from the source to drain electrodes is controlled by relatively low gate voltages. Furthermore, excellent characteristics such as a high current density of approximately 4 mA/cm2 and high-speed operation of less than 0.25 ms are realized by applying a buried Al grid electrode as the Schottky gate.

We have fabricated planar bottom-contact organic thin-film transistors as a function of the thickness of the pentacene active layer. The highest mobility of the planar bottom-contact transistors is 0.47 cm 2 /Vs with only a 7 nm pentacene active layer. Our planar bottom-contact transistors show much higher mobility than conventional bottom-contact counterparts and even higher than the reported mobility values of top-contact counterparts for each thickness in the range from 2.5 to 10 nm. We find that spike at the edges of source and drain electrodes seriously deteriorates device performance.

Static induction transistors (SITs) using copper phthalocyanine films and Al Schottky gate electrode are fabricated and the basic electrical characteristics are investigated. The electrical characteristics show that the current flows from the source to drain electrodes is controlled by the Al gate voltage and a typical SIT operation with non-saturating properties is examined. Furthermore, a high power and high frequency operation as organic transistors is obtained.

We fabricated field-effect transistors (FETs) using donor (TMTSF) and acceptor (TCNQ) stacked layers, and we investigated the change of conductivity in the charge transfer (CT) complex layer by applying gate voltages. Two types of FETs having TMTSF/TCNQ and TCNQ/TMTSF structures are examined. The stacked-layer FET shows a large transconductance compared with a single-layer FET. The experimental results demonstrate that the CT complex layer formed between donor and acceptor films mainly works as a conduction channel. Furthermore, the change in the degree of charge transfer (corresponding to conductivity change) is confirmed by infrared absorption spectra.

We have fabricated photoelectric cells using multi-layered organic dyes and evaluated their photoelectric properties. These cells have both functions of color filtering and bias voltage dependence of the dissociation of photoexcited excitons. The photocurrent spectral sensitivity of the multi-layered cells can be controlled by the bias voltage.

Photoconductivity (PC) measurements were employed to investigate the photoelectric properties of InAs/GaAs strained-layer structure grown on GaAs (100), (311)A and (111)A substrates. PC results of the sample grown on GaAs (311)A and (111)A substrates showed specific PC signals at lower energy region (around 1.2 eV) from GaAs band-edge. From transient PC measurement varying the sample temperature, activation energies of around 0.19 eV were obtained for the sample grown on (311)A substrate with 1 monolayer of InAs. These activation energies suggest the existence of relatively thick InAs region that are locally formed and/or specific defects formed in thesamples grown on highly oriented substrates.

Low-energy (170 eV) C+ ion-beam doping during molecular beam epitaxy of GaAs was carried out using a combined ion beam and molecular beam epitaxy (CIBMBE) system. Incorporated C atoms were both electrically and optically well-activated as acceptors with doping levels up to 4 × 1019 cm−3 in the as-grown condition. In low temperature (2 K) photoluminescence (PL) spectra, C-related specific emissions were clearly observed, indicating good quality of the films. To understand the advantages of low-energy process by CIBMBE, film quality and the rate of C activation were compared with those obtained from 400 keV hot implantation of C at substrate temperatures up to 600°C. Through Raman scattering, 2 K PL and Hall effect measurements, it was found that the use of a low-energy C+ ion beam offers advantages such as low damage doping and good activation rate of incorporated C atoms.

A high-performance vertical-type organic transistor has been fabricated using bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) for the channel layer. The BTQBT molecules are oriented horizontally, with the molecular plane of each monolayer parallel to the substrate. The π–π stacking direction of the BTQBT molecules is aligned with the carrier transport direction in this vertical transistor. The modulated drain current density exceeded 1 A cm−2 upon the application of a gate voltage of less than 5 V. In addition, the device exhibits a high on/off current ratio of over 105.