Showing papers on "Pentacene published in 2002"
TL;DR: In this article, a spin-coated polymer gate dielectric layer was used to obtain a polyvinylphenol-based copolymer-based transistor with a carrier mobility as large as 3 cm2/V's and sub-threshold swing as low as 0.5 V/decade.
Abstract: We have fabricated pentacene organic thin film transistors with spin-coated polymer gate dielectric layers, including cross-linked polyvinylphenol and a polyvinylphenol-based copolymer, and obtained devices with excellent electrical characteristics, including carrier mobility as large as 3 cm2/V s, subthreshold swing as low as 1.2 V/decade, and on/off current ratio of 105. For comparison, we have also fabricated pentacene transistors using thermally grown silicon dioxide as the gate dielectric and obtained carrier mobilities as large as 1 cm2/V s and subthreshold swing as low as 0.5 V/decade.
1,225 citations
TL;DR: In this article, the authors have fabricated organic thin-film transistor (OTFT)-driven active matrix liquid crystal displays on flexible polymeric substrates using a low-temperature process.
Abstract: We have fabricated organic thin-film transistor (OTFT)-driven active matrix liquid crystal displays on flexible polymeric substrates. These small displays have 16×16 pixel polymer-dispersed liquid crystal arrays addressed by pentacene active layer OTFTs. The displays were fabricated using a low-temperature process (<110 °C) on flexible polyethylene naphthalate film and are operated as reflective active matrix displays.
792 citations
TL;DR: In this paper, organic vapor phase deposition was used to grow polycrystalline pentacene channel thin-film transistors, and O2-plasma treated SiO2 was treated with octadecyltrichlorosilane (OTS) prior to Pentacene deposition.
Abstract: Organic vapor phase deposition was used to grow polycrystalline pentacene channel thin-film transistors. Substrate temperature, chamber pressure during film deposition, and growth rate were used to vary the crystalline grain size of pentacene films on O2-plasma treated SiO2 from 0.2 to 5 μm, leading to room-temperature saturation regime field-effect hole mobilities (μeff) from 0.05±0.02 to 0.5±0.1 cm2/V s, respectively. Surface treatment of SiO2 with octadecyltrichlorosilane (OTS) prior to pentacene deposition resulted in μeff⩽1.6 cm2/V s, and drain current on/off ratios of ⩽108 at room temperature, while dramatically reducing the average grain size. X-ray diffraction studies indicate that the OTS treatment decreases the order of the molecular stacks. This suggests an increased density of flat-lying molecules, accompanying the improvement of the hole mobility at the pentacene/OTS interface.
679 citations
TL;DR: A series of 6,13-disubstituted pentacenes, in which the substituents are functionalized ethyne units, were synthesized and analyzed by X-ray crystallography and were highly soluble and oxidatively stable and exhibited a significant amount of pi-stacking in the crystal.
566 citations
IBM1
TL;DR: Organic thin film transistors fabricated by spin-coating this adduct, followed by thermal conversion to pentacene, exhibit the highest mobility reported to date for a solution-processed organic semiconductor.
Abstract: The Lewis acid-catalyzed Diels−Alder reaction of the organic semiconductor pentacene with N-sulfinylacetamide yields a soluble adduct. Spin-coated thin films of this adduct undergo solid-phase conversion to form thin films of pentacene at moderate temperatures. Organic thin film transistors fabricated by spin-coating this adduct, followed by thermal conversion to pentacene, exhibit the highest mobility reported to date for a solution-processed organic semiconductor.
473 citations
TL;DR: The reorganization energy upon positive ionization of pentacenes is determined both experimentally and theoretically to be remarkably low, one key element that allows one to rationalize the extremely high hole mobilities recently measured in pentacene single crystals.
Abstract: The reorganization energy in pentacene is reported on the basis of a joint experimental and theoretical study of pentacene ionization using high-resolution gas-phase photoelectron spectroscopy, semiempirical intermediate neglect of differential overlap calculations, and first-principles correlated quantum-mechanical calculations at MP2 and density functional theory levels. The reorganization energy upon positive ionization of pentacene is determined both experimentally and theoretically to be remarkably low. This is one key element that allows one to rationalize the extremely high hole mobilities recently measured in pentacene single crystals.
418 citations
TL;DR: In this paper, it was shown that when a pentacene thin-film transistor is exposed to humidity, its saturation current decreases and can therefore be used to measure the amount of relative humidity in atmosphere.
Abstract: When a pentacene thin-film transistor is exposed to humidity, its saturation current decreases. This decrease was found to be reversible and can therefore be used to measure the amount of relative humidity in atmosphere. The sensitivity was found to depend on the thickness of the pentacene layer. The microscopic origin of the sensing mechanism is discussed.
366 citations
TL;DR: The hole-vibrational coupling is found to be significantly smaller than the electron-vibational coupling in the case of these oligomers; however, both quantities are predicted to converge to the same value when increasing the chain length.
Abstract: The hole-vibrational coupling is reported for anthracene, tetracene, and pentacene on the basis of a joint experimental and theoretical study of ionization spectra using high-resolution gas-phase photoelectron spectroscopy and first-principles correlated quantum-mechanical calculations. The hole-vibrational coupling is found to be significantly smaller than the electron-vibrational coupling in the case of these oligomers; however, both quantities are predicted to converge to the same value when increasing the chain length.
361 citations
PARC1
TL;DR: In this article, a density of state model for the transport properties of polycrystalline pentacene field effect transistors is presented, and the effect of different localized trap distributions on the current-voltage characteristics of such devices is investigated.
Abstract: We present a density of state model for the transport properties of pentacene field effect transistors. Using a one-dimensional transistor model we study the effect of different localized trap distributions on the current-voltage characteristics of such devices. We find that a distributed trap model with a steep exponential band tail of donors and a shallower exponential tail of acceptors inside the band gap can describe consistently our experimental data obtained from bottom-gate polycrystalline pentacene transistors for different gate dielectrics and under various external conditions.
268 citations
TL;DR: In this paper, the electronic structure of the interfaces formed between pentacene and various metals: Au, Ag, and Ca, using photoemission spectroscopy was examined, and the formation of an interface dipole that varied linearly with the measured metal work function was observed.
Abstract: We examined the electronic structure of the interfaces formed between pentacene and various metals: Au, Ag, and Ca, using photoemission spectroscopy. For all interfaces, we observed the formation of an interface dipole that varied linearly with the measured metal work function. We observed that the behavior of the interfaces of Ca with pentacene was symmetric with respect to whether Ca was deposited on pentacene or vice versa. On the other hand, the interfaces of Au and Ag with pentacene were asymmetric. For both Au and Ag we saw indications that upon metal deposition, metal penetration resulted in a metallic surface with a work function significantly different from that of pure Au or Ag. This also resulted in different interface dipoles for these interfaces.
233 citations
TL;DR: In this paper, a large interface dipole was measured for pentacene on Au(111) (0.95 eV) and a relatively small interface diphole was measured on SnS2 for Pentacene in ultrahigh vacuum.
Abstract: X-ray photoemission, ultraviolet photoemission spectroscopy (UPS), and scanning tunneling microscopy (STM) have been used to determine the energy level alignment and the molecular ordering of monolayer and submonolayer pentacene films on Au(111) in ultrahigh vacuum. Pentacene evaporated onto the van der Waals surface of SnS2 was used as a noninteracting substrate for comparison. A large interface dipole was measured for pentacene on Au(111) (0.95 eV) whereas pentacene on SnS2 showed a relatively small interface dipole (0.26 eV). The different interface dipoles are related to the different orientations of the pentacene molecules due to different pentacene substrate interaction energies. Differences in the UPS spectra also support changing molecular orientations of the two substrates. STM images of pentacene on Au(111) revealed that the molecules lay flat on the substrate and are oriented parallel to each other, forming striped structures that are commensurate with the Au(111) lattice. The pentacene coverag...
TL;DR: In this article, a fully patterned all-organic thin film transistors were fabricated on glass substrates using the conducting polymer poly(3,4-ethylenedioxythiophene) for the gate electrodes and the source and drain contacts, poly-4-vinylphenol and poly-3-hexylthiophene for the organic active layer.
Abstract: We have fabricated fully patterned all-organic thin film transistors on glass substrates using the conducting polymer poly(3,4-ethylenedioxythiophene) for the gate electrodes and the source and drain contacts, poly-4-vinylphenol for the gate dielectric layer, and pentacene or poly-3-hexylthiophene for the organic active layer. All-organic pentacene transistors have carrier mobility as large as 0.1 cm2/V s and threshold voltage of 1 V, similar to pentacene transistors fabricated with high-quality inorganic gate dielectrics and noble-metal contacts. The carrier mobility of all-polymer poly-3-hexylthiophene transistors is somewhat lower compared with that of pentacene transistors, but similar to that of poly-3-hexylthiophene devices made with inorganic metals and dielectrics.
TL;DR: In this article, the flatband voltage for disordered organic field effect transistors is defined as a characterization parameter, and the transfer characteristics of the solution processed organic semiconductors pentacene, poly(2,5-thienylene vinylene) and poly(3-hexyl thiophene) are modeled as a function of temperature and gate voltage with a hopping model.
Abstract: The switch-on voltage for disordered organic field-effect transistors is defined as the flatband voltage, and is used as a characterization parameter. The transfer characteristics of the solution processed organic semiconductors pentacene, poly(2,5-thienylene vinylene) and poly(3-hexyl thiophene) are modeled as a function of temperature and gate voltage with a hopping model in an exponential density of states. The data can be described with reasonable values for the switch-on voltage, which is independent of temperature. This result also demonstrates that the large threshold voltage shifts as a function of temperature reported in the literature constitute a fit parameter without a clear physical basis.
TL;DR: In this article, pseudopotential density-functional calculations for pentacene and anthracene were used to obtain atomic structures, cohesive energies, and surface energies for the low index surfaces.
Abstract: First-principles pseudopotential density-functional calculations for pentacene and anthracene are used to obtain atomic structures, cohesive energies, and surface energies for the low index surfaces. For pentacene, calculations predict that the (001) surface has a much lower surface energy than the other surfaces. From the first-principles results a general model of the intermolecular bonding is developed. This model may be employed to estimate the surface energies and cohesive energy for any polyacene crystal. Implications of the present results for understanding the temperature dependence of the growth morphology of pentacene are discussed.
TL;DR: In this paper, the transfer of a metal film from a stamp to a substrate assisted by cold welding is demonstrated, where the patterned metal film can be used as an etch mask to replicate the pattern on the substrate, or the film itself can serve as contact electrodes for a wide range of electronic devices.
Abstract: We demonstrate a patterning method capable of producing features of submicron scale based on the transfer of a metal film from a stamp to a substrate assisted by cold welding. The patterned metal film can be used as an etch mask to replicate the pattern on the substrate, or the film itself can serve as contact electrodes for a wide range of electronic devices. We demonstrate the versatility of the technique by fabricating a polymer grating on SiO2 with lateral dimensions <80 nm and a pattern resolution approaching 10 nm, and by fabricating organic solar cells and pentacene channel organic thin-film transistors with channel lengths as short as 1 μm.
TL;DR: In this article, the authors measured the characteristics of electronic charge concentrations and the interface traps of the pentacene thin-film transistors, using the capacitance-voltage and deep-level transient spectroscopy (DLTS) measurements.
Abstract: Organic thin-film transistors using the pentacene as an active electronic material have shown the mobility of 0.8 cm2/V s and the grains larger than 1 μm. To study the characteristics of electronic charge concentrations and the interface traps of the pentacene thin films, the capacitance properties were measured in the metal/insulator/organic semiconductor structure device by employing the capacitance–voltage and deep-level transient spectroscopy (DLTS) measurements. Based on the DLTS measurements, the concentrations and the energy levels of hole and electron traps in the obtained pentacene films were formed to be approximately 4.2×1015 cm−3 at Ev+0.24 eV, 9.6×1014 cm−3 at Ev+1.08 eV, 6.5×1015 cm−3 at Ev+0.31 eV and 2.6×1014 cm−3 at Ec−0.69 eV.
TL;DR: In this article, the EHT calculations of the band electronic structure of substituted pentacene derivatives and the polymorphs of the parent compound were performed and the results showed that there are wide disparities among the bandwidths and electronic dimensionalities of these compounds.
Abstract: We report EHT calculations of the band electronic structure of substituted pentacene derivatives and the polymorphs of the parent compound. The results show that there are wide disparities among the bandwidths and electronic dimensionalities of these compounds. The parent pentacene polymorphs are 2-dimensional in their band electronic structure with moderate dispersions; the bandwidths in the 14.1 A d-spacing polymorph are noticeably larger than for the 14.5 A d-spacing polymorph, reported by Campbell. Whereas the parent pentacene polymorphs adopt the well-known herringbone packing, the new, substituted pentacenes are noticeably different in their solid state structures and this is reflected in the band electronic structures. TMS adopts a highly 1-dimensional structure that leads to a large bandwidth along the stacking direction; TIPS also adopts a stacked structure, but because the molecules are laterally interleaved in the fashion of bricks in a wall, this compound is strongly 2-dimensional.
Patent•
28 Jun 2002TL;DR: In this article, a memory cell is constructed using a field effect organic transistor using a ferroelectric thin film polymer as gate dielectric, which can be made from poly(phenylenes), thiophene oligomers, pentacene, polythiophene, perfluoro copper phthalocyanine or other organic thin films.
Abstract: This invention proposes to make memory using organic materials. The basic structure of the memory cell is a field effect organic transistor using a ferroelectric thin film polymer as gate dielectric. By controlling the gate voltage to polarize the thin film ferroelectric polymer polarized in either an “up” or “down” state, the source-drain current can be controlled between two different values under the same source-drain voltage. The source-drain current thus can be used to represent either a “0” or “1” state. The organic thin film transistor can be made from poly(phenylenes), thiophene oligomers, pentacene, polythiophene, perfluoro copper phthalocyanine or other organic thin films. The ferroelectric thin film can be poly(vinylidene fluoride) (PVDF), poly(vinyldiene-trifluoroethylene) (P(VDF-TrFE)) copolymers, odd-numbered nylons, cyanopolymers, polyureas, or other ferroelectric thin films. As the deposition of these organic thin films can be done at temperatures below 200° C., the memory cell can be made on many kinds of substrates including plastics.
TL;DR: In this paper, the authors used measurements of pentacene thin-film transistors to explore hole transport mechanisms and found that the subthreshold characteristics are attributed to deep acceptors in the Pentacene film.
Abstract: Measurements of pentacene thin-film transistors are used to explore hole transport mechanisms. The grain-boundary barrier model does not account for the data, since no field dependence of the mobility is observed over a wide range of gate and drain voltages. Instead, trapping provides a more satisfactory qualitative and quantitative interpretation. The subthreshold characteristics are attributed to deep acceptors in the pentacene film, and the conclusions are supported by numerical modeling.
TL;DR: In this article, the authors present a process which uses a dry organic encapsulant (parylene) as a boundary layer between an organic semiconductor (pentacene) and photolithographic chemicals.
Abstract: Organic semiconductors have demonstrated excellent electrical performance, in some cases rivaling inorganic systems in use today. These materials, which are processed at or near room temperature, have attracted considerable interest because they would enable the creation of active circuitry on organic substrates leading to a new generation of displays, rf identification systems, and smartcards. Many of these materials are intolerant to wet processing, however. This has led to a major processing limitation: the lack of a subtractive photolithographic patterning process to define active regions of the semiconductor. This article presents a process which uses a dry organic encapsulant (parylene) as a boundary layer between an organic semiconductor (pentacene) and photolithographic chemicals. Traditional photolithography may then be performed to use a dry etch to pattern the material stack. This process, which is fully subtractive, opens the path to the use of these materials in a wide range of applications.
TL;DR: In this article, the optical and luminescence properties of pentacene films deposited on n-Si by thermal evaporation at room temperature, 40, 60, 80, and 120
Abstract: We report on the optical and luminescence properties of pentacene films deposited on n-Si by thermal evaporation at room temperature, 40, 60, 80, and 120 °C. Ellipsometric spectra of the films deposited at room temperature and 60 °C exhibited a main absorption peak at 1.82 eV and additional weak features at higher energy levels. Photoluminescence spectra taken at room temperature revealed band-to-exciton and band-to-acceptor transitions at 1.7 and 1.76 eV, respectively. An electroluminescence band was also observed near 1.65 eV under a forward bias from p-pentacene/n-Si diodes which show strong rectifying behavior.
TL;DR: In this paper, the authors measured transient photoconductivity in functionalized pentacene molecular crystals using ultrafast optical pump--terahertz probe techniques, and the single crystal samples were excited using 800 nm, 100 fs pulses.
Abstract: We have measured transient photoconductivity in functionalized pentacene molecular crystals using ultrafast optical pump--terahertz probe techniques. The single crystal samples were excited using 800 nm, 100 fs pulses, and the change in transmission of time-delayed, subpicosecond terahertz pulses was used to probe the photoconducting state over a temperature range from 10 to 300 K. A subpicosecond rise in photoconductivity is observed, suggesting that mobile carriers are a primary photoexcitation. At times longer than 4 ps, a power-law decay is observed consistent with dispersive transport.
Patent•
07 Aug 2002
TL;DR: In this paper, an organic semiconductor thin film suitably employed in electronics, photonics, bioelectronics, or the like, and a method for forming the same is presented.
Abstract: An organic semiconductor thin film suitably employed in electronics, photonics, bioelectronics, or the like, and a method for forming the same. An organic semiconductor solution becoming the material of the organic semiconductor thin film, and an organic semiconductor element employing the organic semiconductor thin film are also provided. The transistor is obtained by forming a gate electrode (2), an insulator layer (3), a source electrode, and drain electrodes (4, 4) sequentially on a glass substrate (5) and then applying o-dichlorobenzene solution of pentacene (0.05% by mass) and drying thereby forming an organic semiconductor thin film (1). Since the organic semiconductor thin film (1) can be formed easily at a low cost and has substantially no defect, a transistor having excellent electronic characteristics can be provided.
TL;DR: The transition from surface to bulk pentacene at the Au(111) interface will have important implications for the mechanism of carrier transport across the interface as mentioned in this paper, where STM observations reveal periodic rows of molecules spaced 61 ± 5 A apart.
Abstract: The transition from surface to bulk pentacene at the Au(111) interface will have important implications for the mechanism of carrier transport across the interface. STM observations of pentacene molecules on the Au(111) surface, at more than a monolayer coverage, revealed periodic rows of molecules spaced 61 ± 5 A apart. These widely spaced periodic rows consist of flat and edge-on molecules aligned with the initial layer of pentacene. Commensuration with the surface and characteristic bulk pentacene−pentacene interactions drive the formation of this unique structure.
TL;DR: In this paper, the authors investigated the nature of the interaction between samarium (Sm) and pentacene, and the energy level alignment at the resulting interfaces using ultraviolet photoelectron spectroscopy.
Abstract: We have investigated the nature of the interaction between samarium (Sm) and pentacene, and the energy level alignment at the resulting interfaces. The valence electronic structure of in situ prepared samples, i.e., pentacene evaporated onto Sm surfaces and vice versa, was investigated with ultraviolet photoelectron spectroscopy. Pentacene appears to physisorb on the metal surface. Sm also appears to interact weakly when evaporated on the organic material, forming clusters at low coverage. Indications of a valence change of Sm upon evolution from clusters to metallic film are found. The highest occupied molecular orbital of pentacene is measured at 1.85 eV below the metal Fermi level EF for both evaporation sequences. Estimating the energy of the lowest unoccupied molecular orbital of pentacene using the transport gap, we obtain a barrier of only 0.35 eV for the injection of electrons from the metal into the organic material.
TL;DR: In this paper, the vibronic spectra of the large organic molecules tetracene (C18H12), pentacene(C24H14), base-free porphin (C20H14N4), and base- free phthalocyanine (C32H18N8) were investigated in large (N≈ 103-104)======4He droplets using laser induced fluorescence.
Abstract: The vibronic spectra of the large organic molecules tetracene (C18H12), pentacene (C24H14), base-free porphin (C20H14N4) and base-free phthalocyanine (C32H18N8) have been investigated in large (N ≈ 103–104)
4He droplets using laser induced fluorescence. The spectra show sharp zero phonon lines (Δν ⩽ 0.2 cm−1), accompanied by weaker phonon wings on the blue side. The very small inhomogeneous broadening of the zero phonon lines supports the unique properties of liquid He as an extremely gentle ultra-cold matrix for high resolution spectroscopy of larger molecules. Pronounced structures in the phonon wings, which are characteristic for each molecule, are attributed to the excitation of vibrational modes of the helium atoms located in shells surrounding the molecule.
TL;DR: In this paper, a solid-state dye-sensitized photovoltaic cell consisting of vacuum deposited pentacene onto ruthenium dye-coated TiO 2 electrode doped with iodine was fabricated.
TL;DR: In this paper, low frequency conductivity noise in the drain-source channel of organic material field-effect transistors was investigated by measuring the spectra of current fluctuations for several values of the gate voltage Vgs and drain voltage Vds and found that it is 1/f.
Abstract: We investigate low frequency conductivity noise in the drain-source channel of organic material field-effect transistors by measuring the spectra of current fluctuations for several values of the gate voltage Vgs and drain voltage Vds and find that it is 1/f. The samples are biased in the ohmic range of the applied Vds. The relative current 1/f noise is inversely proportional to the charge carrier numbers N generated by illumination or by varying the gate-source voltage. Hooge’s empirical relation for the 1/f noise is validated for these organic semiconductors with an α≅0.01 for poly-thienylene vinylene and about 100 for pentacene thin film transistors. From geometry dependence of the noise we conclude that series resistance can be ignored for poly-thienylene vinylene field-effect transistors. However, some pentacene samples suffer from a noisy series resistance to the channel resistance. From the 1/f noise dependence on geometry and gate voltage bias we conclude that it can be used as a diagnostic tool f...
TL;DR: In this article, the pyrolysis of 1,4-bis(phenyliodonio)benzene-2,5-dicarboxylate (9,11,20,22-Tetraphenyltetrabenzo[a,c,l,n]pentacene (4 ) was prepared by the pyria of 1.4-benzadiyne in the presence of phencyclone.
TL;DR: A lattice dynamics calculation to compute the "inherent structures" of minimum potential energy for pentacene, starting from available X-ray data shows that two distinct bulk crystalline phases of pentacenes exist.
Abstract: We have performed a lattice dynamics calculation to compute the “inherent structures” of minimum potential energy for pentacene, starting from available X-ray data. The calculation shows that two d...