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Showing papers on "Pentacene published in 2004"


Journal ArticleDOI
TL;DR: In this article, the hole mobility for the organic conductor pentacene was obtained at room temperature and at 225 K. The number of traps was reduced by two orders of magnitude compared with conventional methods.
Abstract: We have obtained a hole mobility for the organic conductor pentacene of μ=35 cm2/V s at room temperature increasing to μ=58 cm2/V s at 225 K. These high mobilities result from a purification process in which 6,13-pentacenequinone was removed by vacuum sublimation. The number of traps is reduced by two orders of magnitude compared with conventional methods. The temperature dependence of the mobility is consistent with the band model for electronic transport.

856 citations


Journal ArticleDOI
TL;DR: In this paper, a hole mobility for the organic conductor pentacene of 35 cm2/Vs at room temperature increasing to 58 cm2 /Vs at 225k was obtained.
Abstract: We have obtained a hole mobility for the organic conductor pentacene of 35 cm2/Vs at room temperature increasing to 58 cm2/Vs at 225K. These high mobilities result from a purification process in which 6,13-pentacenequinone was removed by vacuum sublimation. The number of traps is reduced by two orders of magnitude compared with conventional methods. The temperature depandence of the mobility is consistent with the band model for electronic transport.

750 citations


Journal ArticleDOI
TL;DR: Perfluoropentacene is a planar and crystalline material that adopts a herringbone structure as observed for pentacene, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.
Abstract: We report the synthesis and characterization of perfluoropentacene as an n-type semiconductor for organic field-effect transistors (OFETs). Perfluoropentacene is a planar and crystalline material that adopts a herringbone structure as observed for pentacene. OFETs with perfluoropentacene were constructed using top-contact geometry, and an electron mobility of 0.11 cm2 V-1 s-1 was observed. Bipolar OFETs with perfluoropentacene and pentacene function at both negative and positive gate voltages. The improved p−n junctions are probably due to the similar d-spacings of both acenes. Complementary inverter circuits were fabricated, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.

676 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss the processes involved in pentacene film growth, emphasizing differences with respect to inorganic films and the influence of growth parameters such as substrate nature and temperature, the deposition rate, and the kinetic energy of the molecular beam on the structure and morphology of Pentacene films.
Abstract: Pentacene stands out as a model molecule among organic semiconductors due to its ability to form well-ordered films that show a high field effect mobility. We discuss the processes involved in pentacene film growth, emphasizing differences with respect to inorganic films. The influence of growth parameters such as the substrate nature and temperature, the deposition rate, and the kinetic energy of the molecular beam on the structure and morphology of pentacene films are discussed. Finally, we overview recent attempts to model pentacene film nucleation and growth, and draw attention to the role of dislocations.

588 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate controllable shift of the threshold voltage and the turn-on voltage in pentacene thin film transistors and rubrene single crystal field effect transistors by the use of nine organosilanes with different functional groups.
Abstract: We demonstrate controllable shift of the threshold voltage and the turn-on voltage in pentacene thin film transistors and rubrene single crystal field effect transistors (FET) by the use of nine organosilanes with different functional groups. Prior to depositing the organic semiconductors, the organosilanes were applied to the SiO2 gate insulator from solution and form a self-assembled monolayer (SAM). The observed shifts of the transfer characteristics range from −2to50V and can be related to the surface potential of the layer next to the transistor channel. Concomitantly the mobile charge carrier concentration at zero gate bias reaches up to 4×1012∕cm2. In the single crystal FETs the measured transfer characteristics are also shifted, while essentially maintaining the high quality of the subthreshold swing. The shift of the transfer characteristics is governed by the built-in electric field of the SAM and can be explained using a simple energy level diagram. In the thin film devices, the subthreshold re...

532 citations


Journal ArticleDOI
TL;DR: In this article, an efficient organic photovoltaic cell based on a heterojunction of pentacene and C60 was fabricated, which exhibited broad light-harvesting throughout the visible spectrum with a peak external quantum efficiency (EQE) of 58±4% at short-circuit condition.
Abstract: We have fabricated an efficient organic photovoltaic cell based on a heterojunction of pentacene and C60. Photocurrent action spectra exhibit broad light-harvesting throughout the visible spectrum with a peak external quantum efficiency (EQE) of 58±4% at short-circuit condition. Modeling studies indicate that this high EQE can be partly attributed to the large exciton diffusion length in the pentacene film as well as efficient dissociation of excitons at the pentacene/C60 heterojunction.

513 citations


Journal ArticleDOI
TL;DR: In this article, the growth of molecular adlayers on solid substrates is reviewed with aspecial emphasis on molecules of relevance for organic electronics, and the importance of the formation of ordered molecular overlayers, which are compared with the structure of the corresponding bulk crystals.
Abstract: The growth of molecular adlayers on solid substrates is reviewed with aspecial emphasis on molecules of relevance for organic electronics. In particular,we will consider planar molecules with extended π-systems, namely acenes (anthracene, tetracene, pentacene), perylene, coronenes, diindenoperylene, 3,4,9,10-perylene-tetracarboxylicacid-dianhydride, poly-phenylenes, oligothiophenes, and phthalocyanines. Special consideration is given to the importance of the formation of ordered molecular overlayers, which are compared with the structure of the corresponding bulk crystals. Whenever possible, aspects relevant for device fabrication (morphology of deposited films, mobilities of charge carriers) will be addressed.

479 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate controllable shift of the threshold voltage and the turn-on voltage in pentacene thin film transistors and rubrene single crystal field effect transistors by the use of nine organosilanes with different functional groups.
Abstract: We demonstrate controllable shift of the threshold voltage and the turn-on voltage in pentacene thin film transistors and rubrene single crystal field effect transistors (FET) by the use of nine organosilanes with different functional groups. Prior to depositing the organic semiconductors, the organosilanes were applied to the SiO2 gate insulator from solution and form a self assembled monolayer (SAM). The observed shift of the transfer characteristics range from -2 to 50 V and can be related to the surface potential of the layer next to the transistor channel. Concomitantly the mobile charge carrier concentration at zero gate bias reaches up to 4*10^12/cm^2. In the single crystal FETs the measured transfer characteristics are also shifted, while essentially maintaining the high quality of the subthreshold swing. The shift of the transfer characteristics is governed by the built-in electric field of the SAM and can be explained using a simple energy level diagram. In the thin film devices, the subthreshold region is broadened, indicating that the SAM creates additional trap states, whose density is estimated to be of order 1*10^12/cm^2.

479 citations


Journal ArticleDOI
TL;DR: R grazing incidence X-ray diffraction reveals that a pentacene monolayer, grown on an amorphous SiO2 substrate that is commonly used as a dielectric layer in organic thin film transistors (OTFTs), is crystalline.
Abstract: Grazing incidence X-ray diffraction reveals that a pentacene monolayer, grown on an amorphous SiO2 substrate that is commonly used as a dielectric layer in organic thin film transistors (OTFTs), is crystalline. A preliminary energy-minimized model of the monolayer, based on the GIXD data, reveals that the pentacene molecules adopt a herringbone arrangement with their long axes tilted slightly from the substrate normal. Although this arrangement resembles the general packing features of the (001) layer in single crystals of bulk pentacene, the monolayer lattice parameters and crystal structure differ from those of the bulk. Because carrier transport in pentacene OTFTs is presumed to occur in the semiconductor layers near the dielectric interface, the discovery of a crystalline monolayer structure on amorphous SiO2 has important implications for transport in OTFTs.

402 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that 6,13-Bis(triisopropylsilylethynyl) pentacene (2) is approximately 50× more stable toward degradation in air-saturated tetrahydrofuran solution as compared to unsubstituted Pentacene.
Abstract: The organic semiconductor pentacene (1) has shown the highest field effect mobilities in thin films of any organic semiconductor, yet suffers from instability toward oxidation. 6,13-Bis(triisopropylsilylethynyl)pentacene (2) has been reported as an interesting functionalized pentacene which is soluble in common organic solvents and exhibits high carrier mobility (>0.1 cm2/Vs) in thin film transistor devices. In our investigations of 2, we were surprised by its remarkable stability in solution. Using UV−vis spectroscopy we observe that under ambient light conditions, 2 is approximately 50× more stable toward degradation in air-saturated tetrahydrofuran solution as compared to unsubstituted pentacene. Previous investigators have implicated oxygen in the mechanism of photodegradation of pentacene. In this study, quantum chemical calculations have been performed which demonstrate that alkynyl functionalization at the 6 and 13 positions reduces the rate of photooxidation in two ways. First, alkynyl substitutio...

388 citations


Journal ArticleDOI
TL;DR: In this article, the authors quantify the influence of the roughness of the dielectric on the mobility of pentacene transistors and discuss the cause of the effect of roughness on the performance of organic thin-film transistors.
Abstract: The properties of the dielectric strongly influence the performance of organic thin-film transistors. In this letter, we show experimental results that quantify the influence of the roughness of the dielectric on the mobility of pentacene transistors and discuss the cause of it. We consider the movement of charge carriers out of the “roughness valleys” or across those valleys at the dielectric–semiconductor interface as the limiting step for the roughness-dependent mobility in the transistor channel.

Journal ArticleDOI
TL;DR: In this article, the authors fabricated organic thin-film transistors and ring oscillators on paper and on flexible polyetherether ketone film using small-molecule hydrocarbon pentacene as the semiconductor and solution-processed polyvinylphenol as the gate dielectric.
Abstract: We have fabricated organic thin-film transistors and ring oscillators on paper and on flexible polyetherether ketone film using small-molecule hydrocarbon pentacene as the semiconductor and solution-processed polyvinylphenol as the gate dielectric. Transistors on paper have a carrier mobility of 0.2 cm2/V s and an on/off current ratio of 106, similar to devices on polyetherether ketone. A signal propagation delay of 22 μs per stage was measured for pentacene ring oscillators on polyetherether ketone film, and a signal delay of 12 ms was obtained for ring oscillators on paper.

Journal ArticleDOI
TL;DR: Single-crystal field effect transistors of the organic semiconductor dithiophene-tetrathiafulvalene (DT-TTF) were prepared by drop casting and the highest hole mobility observed was 1.4 cm2/Vs, which is the highest reported for an Organic semiconductor not based on pentacene.
Abstract: Single-crystal field effect transistors of the organic semiconductor dithiophene-tetrathiafulvalene (DT-TTF) were prepared by drop casting. Long, thin crystals connected two microfabricated gold electrodes, and a silicon substrate was used as a back gate. The highest hole mobility observed was 1.4 cm2/Vs, which is the highest reported for an organic semiconductor not based on pentacene. A high ON/OFF ratio of at least 7 x 105 was obtained for this device.

Journal ArticleDOI
TL;DR: In this article, gated four-probe measurements were designed to measure contact resistance in pentacene-based organic thin-film transistors (OTFTs) and the potential profiles as a function of contact metallurgy (Pt, Au, Ag, and Ca), substrate chemistry, VG, and temperature were investigated.
Abstract: We describe gated four-probe measurements designed to measure contact resistance in pentacene-based organic thin-film transistors (OTFTs) The devices consisted of metal source and drain electrodes contacting a 300-A-thick pentacene film thermally deposited on Al2O3 or SiO2 dielectrics with a p-doped Si substrate serving as the gate electrode Voltage-sensing leads extending into the source-drain channel were used to monitor potentials in the pentacene film while passing current during drain voltage (VD) or gate voltage (VG) sweeps We investigated the potential profiles as a function of contact metallurgy (Pt, Au, Ag, and Ca), substrate chemistry, VG, and temperature The contact-corrected linear hole mobilities were as high as 175cm2∕Vs and the film sheet resistance and specific contact resistance were as low as 600kΩ∕◻ and 13kΩ-cm, respectively, at high gate voltages In the temperature range of 50–200K, the pentacene OTFTs displayed an activated behavior with activation energies of 15–30meV Importa

Journal ArticleDOI
TL;DR: In this article, the authors review recent work on organic molecular beam deposition (OMBD) with emphasis on growth studies beyond the first monolayer, i.e. the evolution of the film structure and morphology.
Abstract: We review recent work on organic molecular beam deposition (OMBD) with emphasis on growth studies beyond the first monolayer, i.e. the evolution of the film structure and morphology. First, we briefly discuss general issues related to growth physics, including epitaxial relations, surface and interface energies, growth modes, correlation functions, dynamic scaling, and growth exponents. We also point out the general features that distinguish organic systems from inorganic systems, such as the different interaction potentials and the internal degrees of freedom of organic molecules. Then we discuss selected case studies, organised according to the role of the substrate (insulators, metals, semiconductors), covering examples from various organic semiconductors, namely perylene-derivatives (in particular diindeno-perylene (DIP) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)), phthalocyanines, and oligoacenes (anthracene, tetracene, pentacene). Finally, we briefly discuss organics-based heterostructures and indicate some open problems and future directions. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Journal ArticleDOI
TL;DR: In this paper, single crystal high mobility organic field-effect transistors were prepared on prefabricated substrates using a "flip-crystal" approach, which minimized crystal handling and avoided direct processing of the crystal that may degrade the field effect transistors' electrical characteristics.
Abstract: We report on single crystal high mobility organic field-effect transistors prepared on prefabricated substrates using a “flip-crystal” approach. This method minimizes crystal handling and avoids direct processing of the crystal that may degrade the field-effect transistors' electrical characteristics. A chemical treatment process for the substrate ensures a reproducible device quality. With limited purification of the starting materials, hole mobilities of 10.7, 1.3, and 1.4cm2∕Vs have been measured on rubrene, tetracene, and pentacene single crystals, respectively. Four-terminal measurements allow for the extraction of the “intrinsic” transistor channel resistance and the parasitic series contact resistances. The technique employed in this study shows potential as a general method for studying charge transport in field-accumulated carrier channels near the surface of organic single crystals.

Journal ArticleDOI
TL;DR: In this paper, high-performance organic thin-film transistors (OTFTs) with a nanoparticle composite dielectric layer have been demonstrated, which consists of cross-linked poly-4-vinylphenol (PVP) and high-dielectric titanium dioxide (TiO2) nanoparticles.
Abstract: High-performance organic thin-film transistors (OTFTs) with a nanoparticle composite dielectric layer have been demonstrated. The dielectric layer consists of cross-linked poly-4-vinylphenol (PVP) and high-dielectric titanium dioxide (TiO2) nanoparticles. Because of the nanosize of TiO2, it disperses well in the organic solvent, which makes it possible to use solution-processable methods to prepare the dielectric layer. OTFTs with pentacene as the semiconducting layers have been demonstrated; it was found that the OTFTs with the nanocomposite dielectric layer have higher field-induced current than that of conventional devices because the dielectric constant of the gate insulator is increased. This finding opens an interesting direction for the preparation of high-performance OTFTs without complicated sputtering of high-κ dielectric materials.

Journal ArticleDOI
TL;DR: In this article, a field-effect transistor with polycrystalline pentacene films and calcium source-drain electrodes was evaluated in an oxygen-free condition and showed typical ambipolar characteristics and field effect hole mobility of 4.5×10−4cm2/Vs.
Abstract: Field-effect transistors consisted of vacuum-sublimed polycrystalline pentacene films and calcium source-drain electrodes were prepared and device characteristics were evaluated in an oxygen-free condition. The field-effect transistor showed typical ambipolar characteristics and field-effect hole mobility of 4.5×10−4cm2/Vs and field-effect electron mobility of 2.7×10−5cm2∕Vs were estimated from saturation currents. Appearance of an electron enhancement mode in pentacene field-effect transistors was ascribed to the lowering of barrier for electron injection at source-drain electrodes. Effective elimination of electron traps using an oxygen-free condition was found to be another requirement for the observation of ambipolar behavior in pentacene.

Journal ArticleDOI
TL;DR: In this paper, the authors used a heterostructure with pentacene as hole-transport and N,N′-Ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13H27) as electrontransport material, and showed that simultaneous p-and n-channel formation can be observed in a single device.
Abstract: Ambipolar charge injection and transport are a prerequisite for a light-emitting organic fieldeffect transistor (OFET). Organic materials, however, typically show unipolar charge-carrier transport characteristics. Consequently, organic thin-film field-effect transistors based on a single material as active layer can typically either be operated as p- or as n-channel device. In this article we show that by using a heterostructure with pentacene as hole-transport and N,N′-Ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13H27) as electron-transport material, ambipolar characteristics, i.e., simultaneous p- and n-channel formation, can be observed in a single device. An OFET structure is investigated in which electrons and holes are injected from Mg top and Au bottom contacts into the PTCDI-C13H27 and pentacene layers, respectively. Our device exhibits electron and hole mobilities of 3×10−3 and 1×10−4 cm2/V s, respectively. This device architecture serves as a model structure for ambipolar field-e...

Journal ArticleDOI
TL;DR: In this article, optical and electrical measurements on pentacene single crystals were used to extract the density of states in the highest occupied molecular orbital-lowest unoccupied molecular orbital band gap, and it was found that these highly purified crystals possess band tails broader than those typically observed in inorganic amorphous solids.
Abstract: We show that optical and electrical measurements on pentacene single crystals can be used to extract the density of states in the highest occupied molecular orbital-lowest unoccupied molecular orbital band gap. It is found that these highly purified crystals possess band tails broader than those typically observed in inorganic amorphous solids. Results on field-effect transistors fabricated from similar crystals imply that the gap state density is much larger within 5-10 nm of the gate dielectric. Thus, organic thin-film transistors for such applications as flexible displays might be significantly improved by reducing these defects.

Journal ArticleDOI
TL;DR: In this article, single crystal high mobility organic field effect transistors (OFETs) were prepared on prefabricated substrates using a "flip-crystal" approach.
Abstract: We report on single crystal high mobility organic field-effect transistors (OFETs) prepared on prefabricated substrates using a "flip-crystal" approach. This method minimizes crystal handling and avoids direct processing of the crystal that may degrade the FET electrical characteristics. A chemical treatment process for the substrate ensures a reproducible device quality. With limited purification of the starting materials, hole mobilities of 10.7, 1.3, and 1.4 cm^2/Vs have been measured on rubrene, tetracene, and pentacene single crystals, respectively. Four-terminal measurements allow for the extraction of the "intrinsic" transistor channel resistance and the parasitic series contact resistances. The technique employed in this study shows potential as a general method for studying charge transport in field-accumulated carrier channels near the surface of organic single crystals.

Journal ArticleDOI
TL;DR: In this paper, an organic field effect transistor with pentacene active material and a ferroelectric copolymer poly (vinylidene fluoride-trifluoroethylene) as the gate insulator was fabricated.
Abstract: Organic field-effect transistors were fabricated with pentacene as the active material and a ferroelectric copolymer poly(vinylidene fluoride–trifluoroethylene) as the gate insulator. As-prepared devices showed normal p-type transistor operation. The ON- and OFF-states could be written to the device by applying appropriate voltages to the gate with respect to short-circuited source and drain electrodes. The devices exhibited excellent memory retention properties.

Journal ArticleDOI
TL;DR: In this paper, several methods are used in order to extract the mobility and threshold voltage from the transfer characteristic of organic field-effect transistors, which are found to depend on the gate voltage.
Abstract: Organic field-effect transistors were fabricated with vapor-deposited pentacene on aluminum oxide insulating layers. Several methods are used in order to extract the mobility and threshold voltage from the transfer characteristic of the devices. In all cases, the mobility is found to depend on the gate voltage. The first method consists of deriving the drain current as a function of gate voltage (transconductance), leading to the so-called field-effect mobility. In the second method, we assume a power-law dependence of the mobility with gate voltage together with a constant contact resistance. The third method is the so-called transfer line method, in which several devices with various channel length are used. It is shown that the mobility is significantly enhanced by modifying the aluminum oxide layer with carboxylic acid self-assembled monolayers prior to pentacene deposition. The methods used to extract parameters yield threshold voltages with an absolute value of less than 2 V. It is also shown that there is a shift of the threshold voltage after modification of the aluminum oxide layer. These features seem to confirm the validity of the parameter-extraction methods.

Journal ArticleDOI
TL;DR: In this paper, the authors used polyimide gate dielectric layers to fabricate high-quality pentacene field effect transistors on polyethylenenaphthalate-based films.
Abstract: Polyimide gate dielectric layers cured at 180 °C have been employed to fabricate high-quality pentacene field-effect transistors on polyethylenenaphthalate-based films. The surface roughness (root-mean square) of gate dielectric layers characterized by atomic force microscopy is only 0.2 nm, while that of the base film is 1 nm. The transistors with pentacene channel layers deposited on 990 nm polyimide gate dielectric layers attain the on/off ratio of 106 and mobility of 0.3 cm2/V s. Furthermore, by decreasing the thickness of polyimide gate dielectric layers down to 540 nm, the mobility is enhanced up to 1 cm2/V s.

Journal ArticleDOI
TL;DR: In this paper, the authors have fabricated pentacene-based thin film transistors and analyzed their electrical properties with the help of two-dimensional drift-diffusion simulations which favorably compare with the experimental results.
Abstract: We have fabricated pentacene-based thin film transistors and analyzed their electrical properties with the help of two-dimensional drift-diffusion simulations which favorably compare with the experimental results. We have set up a model considering the polycrystalline nature of pentacene and the presence of grains and grain boundaries. We show how this model can be applied to different devices with different grain sizes and we analyze the relationship between mobility, grain size and applied gate voltage. On the basis of the simulation results, we can introduce an effective carrier mobility, which accounts for grain-related effects. The comparison between experimental results and simulations allows us to clearly understand the differences in the mobility derived by the analysis of current-voltage curve (as done experimentally by using standard MOSFET theory) and the intrinsic mobility of the organic layer. The effect of the pentacene/oxide interface traps and fixed surface charges has also been considered. The dependence of the threshold voltage on the density and energy level of the trap states has been outlined.

Journal ArticleDOI
TL;DR: The volume of the unit cell in the thin film phase is almost identical to that of the bulk phase, thus the molecular packing efficiency is effectively the same in both phases as discussed by the authors.
Abstract: Grazing incidence x-ray diffraction, x-ray reflectivity and atomic force microscopy have been performed to study the structure of pentacene thin films on oxidized Si substrates from submonolayer to multilayer coverages. The volume of the unit cell in the thin film phase is almost identical to that of the bulk phase, thus the molecular packing efficiency is effectively the same in both phases. The structure forming from the first monolayer remains the same for films at least 190A thick. The in-plane structure of the submonolayer islands also remains unchanged within a substrate temperature range of 0

Journal ArticleDOI
TL;DR: It is found that due to the steric, polarizable environment and the structural changes induced by local intermolecular charge delocalization, the calculated lambdareorg for DT-TTF decreases, which is of the same order of the previously reported value found for the isolated pentacene molecule.
Abstract: We report on a computational study to understand the high mobility found in dithiophene-tetrathiafulvalene (DT-TTF) transistors, with respect to that known for pentacene, using an extended measure of the reorganization energy (λreorg). We demonstrate the high importance of considering intermolecular interactions to assess hole-hopping mobilities. We find that due to the steric, polarizable environment and the structural changes induced by local intermolecular charge delocalization, the calculated λreorg for DT-TTF decreases from 0.574 eV in the isolated molecule to 0.042 eV in the crystal embedded molecule, which is of the same order of the previously reported value found for the isolated pentacene molecule, 0.098 eV.

Journal ArticleDOI
TL;DR: In this paper, the surface conductivity of pentacene and rubrene single crystals laminated on polarized and nearly unpolarized molecular monolayers with application of perpendicular electric fields was measured.
Abstract: The surface conductivity is measured by a four-probe technique for pentacene and rubrene single crystals laminated on polarized and nearly unpolarized molecular monolayers with application of perpendicular electric fields. The polarization of the self-assembled monolayers (SAMs) shifts the threshold gate voltage, while maintaining a very low subthreshold swing of the single-crystal devices (0.11 V∕decade). The results, excluding influences of parasitic contacts and grain boundaries, demonstrate SAM-induced nanoscale charge injection up to ∼1012cm−2 at the surface of the organic single crystals.

Journal ArticleDOI
TL;DR: In this paper, the surface conductivity of pentacene and rubrene single-crystals laminated on polarized and nearly unpolarized molecular monolayers with application of perpendicular electric fields was measured.
Abstract: The surface conductivity is measured by a four-probe technique for pentacene and rubrene single-crystals laminated on polarized and nearly unpolarized molecular monolayers with application of perpendicular electric fields. The polarization of the self-assembled monolayers (SAMs) shifts the threshold gate voltage, while maintaining a very low subthreshold swing of the single-crystal devices (0.11 V/decade). The results, excluding influences of parasitic contacts and grain boundaries, demonstrate SAM-induced nanoscale charge injection up to ~10^12 cm^-2 at the surface of the organic single crystals.

Journal ArticleDOI
TL;DR: In this article, the authors showed that the barrier to charge injection may depend not only on interactions at the complex triple interface but also on the details of the electronic structure at the semiconductor/dielectric interface.
Abstract: This letter reports on the unexpected dependence of contact resistance on the dielectric layer for pentacene thin film transistors with printed organic conducting electrodes. While the intrinsic mobility is weakly reliant on the dielectric, the contact resistance does vary considerably with dielectric layer. We show that while morphological changes are not apparent, contact resistances vary by an order of magnitude. This result suggests that the barrier to charge injection may depend not only on interactions at the complex triple interface but also on the details of the electronic structure at the semiconductor/dielectric interface.