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A modeling of organic field-effect transistors' (OFETs') electrical characteristics is presented. This model is based on a one-dimensional (1-D) Poisson's equation solution that solves the potential profile in the organic semiconducting film. Most importantly, it demonstrates that, due to the common open-surface configuration used in organic transistors, the conduction occurs in the film volume below threshold. This is because the potential at the free surface is not fixed to zero but rather rises also with the gate bias. The tail of carrier concentration at the free surface is therefore significantly modulated by the gate bias, which partially explains the gate-voltage dependent contact resistance. At the same time in the so-called subthreshold region, we observe a clear charge trapping from the difference between C-V and I-V measurements; hence a traps study by numerical simulation is also performed. By combining the analytical modeling and the traps analysis, the questions on the C-V and I-V characteristics are answered. Finally, the combined results obtained with traps fit well the experimental data in both pentacene and bis(triisopropylsilylethynyl)-pentacene OFETs. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) suffer from limitations such as low mobility of charge carriers and high access resistance. Direct and accurate evaluation of these quantities becomes crucial for understanding the OFETs properties. We introduce the Y function method (YFM) to pentacene OFETs. This method allows us to evaluate the low-field mobility without the access or contact resistance influence. The low-field mobility is shown to be more appropriate than the currently applied field-effect mobility for the OFETs’ performance evaluation. Its unique advantage is to directly suppress the contact resistance influence in individual transistors, although such contact resistance is a constant as compared to the widely accepted variable one with respect to the gate voltage. After a comparison in detail with the transmission-line method, the YFM proved to be a fast and precise alternative method for the contact resistance evaluation. At the same time, how the contact resistance affects the effective mobility and the field-effect mobility in organic transistors is also addressed. [ABSTRACT FROM AUTHOR]

A single-grain organic field-effect transistor (OFET) of pentacene with a 1 μm channel length of top-contact electrodes is demonstrated in a wide range of temperatures from 300 down to 5.8 K. No hysteresis behavior was observed in the transfer characteristics throughout the entire temperature range. The saturation mobility and on/off ratio are estimated at 1.11 cm2/V s and 107 at 300 K and 0.34 cm2/V s and 105 at 5.8 K, respectively. The nonmonotonic temperature dependence of the mobility indicates a bandlike transport at high temperatures. The electric-field dependence of the mobility in the single-grain OFET does not show a Poole-Frenkel-like behavior. This indicates that Poole-Frenkel-like behavior observed in conventional OFETs can be attributed to the disorder of molecules; single-grain OFET is free from such disorders. [ABSTRACT FROM AUTHOR]

A single-grain pentacene field-effect transistor with ordinary top-contact structure is fabricated, and its electrical properties are characterized at various temperatures. The device exhibits field-effect mobility as high as 2 cm2/V s at 300 K, although mobility is dependent on gate voltage. This value for field-effect mobility is about one order of magnitude higher than that of a polycrystalline device made from the same pentacene film. The activation energy obtained from an Arrhenius plot of mobility is nearly constant with varying gate voltage, whereas the activation energy of the polycrystalline device decreases as gate voltage increases. Such behavior of the activation energy suggests that intrinsic carrier transport in an organic grain can be described by thermally activated hopping of molecular polarons while extrinsic transport across grain boundaries can be described by the trap model. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Biomaterials have gained increasing attention in the fabrication of a variety of flexible electronics due to their tunable solubility, robust mechanical property, multi-active binding sites, and excellent biocompatible and biodegradable characterization as well. Here, we review the recent progress of bio-based materials in flexible sensors, mainly describe nature biomaterials (silk fibroin, cellulose and chitin) and chemical-synthesized biomaterials as well as their applications in health monitors, biosensor, human-machine interactions (HMIs) and more, and highlight the current opportunities and challenges that lay ahead in mounting numbers of academia and industry. Furthermore, we expect this review could contribute to unveiling the potentials of developing outstanding and eco-friendly sensors with biomaterials by utilization of printing techniques. [ABSTRACT FROM AUTHOR]

We explore the device physics of thin film transistors (TFTs) with non-Ohmic contacts and develop a simple and fast method for evaluating the contact properties TFTs through output characteristics. Using one single output scan, the quantitative relationship between contact resistances and drain voltage were evaluated, revealing the property of interfacial injection at non-Ohmic contacts. This is demonstrated and validated in both TFT simulations and experiments employing inorganic and organic TFTs. The approach can be applied to general TFTs with arbitrary materials and configurations conveniently and enables faster and improved understanding of TFT operation and device physics. [ABSTRACT FROM AUTHOR]

Printing semiconductor devices under ambient atmospheric conditions is a promising method for the large-area, low-cost fabrication of flexible electronic products. However, processes conducted at temperatures greater than 150 °C are typically used for printed electronics, which prevents the use of common flexible substrates because of the distortion caused by heat. The present report describes a method for the room-temperature printing of electronics, which allows thin-film electronic devices to be printed at room temperature without the application of heat. The development of π-junction gold nanoparticles as the electrode material permits the room-temperature deposition of a conductive metal layer. Room-temperature patterning methods are also developed for the Au ink electrodes and an active organic semiconductor layer, which enables the fabrication of organic thin-film transistors through room-temperature printing. The transistor devices printed at room temperature exhibit average field-effect mobilities of 7.9 and 2.5 cm2 V−1 s−1 on plastic and paper substrates, respectively. These results suggest that this fabrication method is very promising as a core technology for low-cost and high-performance printed electronics. [ABSTRACT FROM AUTHOR]

The frequency response characteristics of semiconductor devices play an essential role in the high-speed operation of electronic devices. We investigated the temperature dependence of dynamic characteristics in pentacene-based organic field-effect transistors and metal-insulator-semiconductor capacitors. As the temperature decreased, the capacitance-voltage characteristics showed large frequency dispersion and a negative shift in the flat-band voltage at high frequencies. The cutoff frequency shows Arrhenius-type temperature dependence with different activation energy values for various gate voltages. These phenomena demonstrate the effects of charge trapping on the frequency response characteristics, since decreased mobility prevents a fast charge response for alternating current signals at low temperatures. [ABSTRACT FROM AUTHOR]

We describe the mechanism of contact resistance reduction and improvement in device performance of organic field-effect transistors by chemical doping at the contact interface. Insertion of iron(III)trichloride into the contact interface significantly reduced the contact resistance from 200 to 8.8 kΩ cm at a gate voltage of -40 V, and a field-effect mobility of 7.0 cm2/V s was achieved in devices based on dioctylbenzothienobenzothiophene. The improved charge injection is attributable to a reduction in the depletion layer thickness at the contact interface and occupation of trap states in the access region due to the generation of charge carriers by contact doping. [ABSTRACT FROM AUTHOR]

Abstract: A development of the conventional transfer-length method (TLM) for organic transistors’ contact resistance evaluation is proposed. By adding the dissipated power in access resistance and in the channel, we found that TLM can be extended to the non-linear region, i.e., up to saturation regime, which is widely believed to be a barrier for TLM application now. To improve the extraction accuracy and stability, a modified TLM version is used for the operation at small gate voltages. This modified power TLM is applied to polymer and pentacene field-effect transistors and proved as a useful tool for the contact resistance evaluation as a function of gate and drain voltages from common current–voltage characterizations. [Copyright &y& Elsevier]

Abstract: Measurements of power spectral density (PSD) of low-frequency noise (LFN) in pentacene field-effect transistors reveal the preponderance of a 1/f-type PSD behavior with the amplitude varying as the squared transistor gain and increasing as the inverse of the gate surface area. Such features impose an interpretation of LFN by carrier number fluctuations model involving capture/release of charges on traps uniformly distributed over the gate surface. The surface slow trap density extracted by the noise analysis is close to the surface states density deduced independently from static I(V) data, which confirms the validity of the proposed LFN interpretation. Further, we found that the trap densities in bottom-contact (BC) devices were higher than in their top-contact (TC) counterparts, in agreement with observations of a poorer crystal structure of BC devices, in the contact regions in particular. At the highest bias the noise originating from the contact resistance is also shown to be a dominant component in the PSD, and it is well explained by the noise originating from a gate-voltage dependent contact resistance. A gate area scaling was also performed, and the good scaling and the dispersion at the highest bias confirm the validity of the applied carrier number fluctuations model and the predominant contact noise at high current intensities. [Copyright &y& Elsevier]

The enhancement of the charge injection process by the insertion of an ultrathin (∼1 nm) contact oxide interlayer (COI) at the metal/organic material interface in organic field effect transistors (OFETs) is reported. Six different oxides were used as COI, and Al2O3 was found to exhibit the highest OFET mobility with a reduction in the average contact resistance (Rc) from 19.9 to 1.9 kΩ·cm. Photoelectron yield spectroscopy analysis revealed that the insertion of COI increases the work function of an Au contact and reduces the charge injection barrier at the interface, which lowers Rc and, therefore, results in enhanced device performance. [ABSTRACT FROM AUTHOR]

We report the effect of air exposure on charge injection process through the metal/organic interface in organic field-effect transistors. Pentacene-based field-effect transistors and metal-insulator-semiconductor capacitors having gold or copper contact were fabricated without exposing to air. An air exposure caused remarkable improvement on the electrical characteristics of the devices, particularly on the contact resistance and frequency response characteristics. Measurements of photoelectron yield spectroscopy revealed that natural oxidation significantly shifted the work function of contact metal and thus charge injection efficiency was improved. This result provides critical insights on control of desirable metal/organic interface in organic electronics devices. [ABSTRACT FROM AUTHOR]

We investigate the effect of the parasitic access resistance on device parameters, particularly the threshold voltage (VT) and the contact resistance (RC), of staggered organic field-effect transistors by varying the active layer thickness (ds). At low gate voltages, RC decreases as ds increases due to the free carrier density increasing in the semiconductor film. At high gate voltages, RC increases as ds increases due to increasing access resistance. These factors degrade the device parameters with increasing ds. The contribution of the change in ds on the VT shift is assessed by subtracting the contact effect from the apparent VT. [ABSTRACT FROM AUTHOR]

The charge injection efficiency of organic field-effect transistors (OFETs) is found to be a critical factor determining the subthreshold characteristics of these devices. OFETs fabricated using a wide band gap organic semiconductor and gold source/drain contacts display large threshold voltage and poor subthreshold characteristics. Insertion of a metal-oxide charge injection layer at the contact/semiconductor interface lower the injection barrier height, resulting in marked improvements in threshold voltage and subthreshold slope and strong suppression of the short-channel effect. The improved subthreshold characteristics are attributed to enhanced charge injection and the consequent promotion of charge accumulation. [ABSTRACT FROM AUTHOR]

A bottom-up fabrication technique for the preparation of self-organized organic field-effect transistors (OFETs) on flexible plastic substrates is presented. Solution-based self-organization of OFETs is achieved by patterning the insulator surface with solution-wettable and unwettable regions. The proposed method satisfies several important requirements of printable electronics, including reduction in energy consumption, minimization of facilities, and the on-demand use of molecular materials. Self-organized OFETs display an average mobility of 0.53 cm2/(V s), on/off ratio of 109, and subthreshold slope of 0.18 V/dec, with near-zero and narrowly distributed threshold voltage. An inverter circuit prepared using these devices is demonstrated with high signal gain. [ABSTRACT FROM AUTHOR]

Semiconductor channels of organic field-effect transistors have been directly self-organized from a solution phase. The alkyl-modified surface was locally patterned by using a phenyl self-assembled monolayer (SAM) for the channels. Drop-cast small organic molecules were selectively crystallized on the phenyl SAM region. The self-organized process allows the simultaneous formation of polycrystalline transistor arrays from the patterned channels. The phenyl SAM under the channel is critical for the improvement of device stability. Further optimization of the deposition process realized direct growth of a single crystal channel from solution between prefabricated electrodes, and the single-crystal transistors exhibited excellent performance. [ABSTRACT FROM AUTHOR]

The effect of semiconductor crystal structure on the performance of organic field-effect transistors is investigated through the fabrication and characterization of devices based on single porphyrin crystals with different center metals. The field-effect mobility of the transistors is found to increase with decreasing intermolecular distance, attributable to greater overlap of π orbitals among close-packed molecules and the consequent promotion of charge transport. [ABSTRACT FROM AUTHOR]

The charge injection process in top-contact organic field-effect transistors was energetically observed with displacement of the Fermi level as a result of scanning the gate voltage. Doping of charge-transfer molecules into the metal/organic interface resulted in low interface resistance, which unveiled the bulk transport of the injected charges from the contact metal into the channel. The authors found that the bulk transport clearly obeys the Meyer-Neldel rule, according to which the exponential density of states near the band edge limits the charge injection. [ABSTRACT FROM AUTHOR]

Frequency response measurements were performed on top-contact pentacene organic thin-film transistors (OTFTs). The ac characteristics of OTFTs are strongly limited by the contact interface between a metallic electrode and a pentacene thin film. Local doping of a charge transfer molecule (CTM) into the contact interface efficiently improves the ac characteristics. Metal-insulator-semiconductor capacitance measurements revealed that the interface contains parasitic impedance composed of capacitance and resistance in parallel. The parasitic impedance was suppressed by CTM doping of the interface. The limitation factors for the frequency of operation in such an OTFT are discussed based on the experimental results and an equivalent circuit model. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors are fabricated using oligomers composed of alternating connected thiophene and furan, and those having alkyl substituents at both ends of the molecules. The mobilities are determined by the transfer line method to correct for the effect of source/drain parasitic resistance. A mobility of 0.042 cm2/V s is achieved for a thienyl-furan oligomer composed of five heterocycles and having hexyl groups at the terminal rings. The mobility of the oligomers strongly depends on the length of the π-conjugated chain and the alkyl chain substituent at both ends, attributable to the specific structural and morphological properties of the vacuum-deposited films. [ABSTRACT FROM AUTHOR]

The origin of intrinsic operational instability in organic field‐effect transistors (OFETs) is discussed by comparing bias stress effects of OFETs with unidirectionally aligned and unaligned active layers of two different semiconducting polymers under vacuum environment. By forming hydrophobic nano‐groove structures on gate dielectric surfaces, a high‐mobility donor–acceptor copolymer, poly[4‐(4,4‐dihexadecyl‐4H‐cyclopenta[1,2‐b:5,4‐b′]‐dithiophen‐2‐yl)‐alt‐[1,2,5]thiadiazolo[3,4‐c]pyridine] (PCDTPT) and a benchmark semicrystalline polymer, poly(2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT‐C16), are successfully aligned. The mobilities of the PCDTPT‐OFETs are higher than those of the PBTTT‐OFETs, but the operational stabilities are lower. Moreover, for both semiconducting polymers, the aligned OFETs exhibit higher mobility but lower operational stability than the unaligned OFETs. These results indicate that an increase in mobility does not necessarily lead to an increase in operational stability. The interface trap density of states analysis reveals that the lower operational stability of PCDTPT‐OFETs is not due to the tail state change but primarily due to the much larger turn‐on voltage shift (ΔVon). The major mechanism causing ΔVon should be the charge carrier transfer from the channel to the gate dielectric. Since the energy barrier limiting the charge carrier transfer decreases with increasing ionization potential of the active layer, the lower operational stability of PCDTPT‐OFETs is attributed to the higher ionization potential of PCDTPT. [ABSTRACT FROM AUTHOR]

A correction to the article "Frequency response analysis of pentacene thin-film transistors with low impedance contact by interface molecular doping" is presented.

T. Minari, M. Kanehara, and co‐workers report a method for the room‐temperature printing of electronics using gold nanoparticles, enabling semiconductor devices to be printed without the application of heat. On page 4886, organic thinfilm transistors are formed on plastic and paper through room‐temperature printing, producing devices with mobilities of 7.9 and 2.5 cm2 V−1 s−1, respectively. The proposed approach permits the printing of devices on any heat‐sensitive substrate, such as plastic, paper, or biomaterials. [ABSTRACT FROM AUTHOR]

Flexible transparent conductors (TCs) are the fundamental components for emerging soft optoelectronics because of their excellent optical, electrical, and mechanical properties. These properties are attributed to reasonable alignment of conductive functional nanomaterials, especially 1D inorganic nanowires. Although various patterning technologies are proposed, patterning highly transparent conductors with satisfactory conductivity and flexibility in a facile, scalable, and versatile manner remains an open issue. Here, a directed self‐assembly strategy is presented for patterning silver nanowires (AgNWs) into flexible TCs with a cross‐linked network structure using microflow velocity‐field‐induced alignment at a liquid–solid interface. Under dual‐surface architectonics, the periodically varying internal microflow in the overcoated AgNW suspension facilitates the spontaneous alignment of the AgNWs on the designated regions in a layer‐by‐layer manner, yielding highly ordered AgNW TCs with an ultrahigh transmittance (98.2%), low sheet resistance (29.7 Ω sq−1), and prominent mechanical deformability. The proposed strategy is further applied to fabricate high‐accuracy arbitrary AgNW circuits to realize flexible transparent heaters with adjustable localized heat sources. This is a universal and customizable method for producing functional nanomaterials with hardly any scale or shape limitations in a streamlined fashion and provides great freedom for prototyping and manufacturing high‐performance soft optoelectronics. [ABSTRACT FROM AUTHOR]

In this work, we systematically investigated the carrier transport of hysteresis-free amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) incorporating high- k (HfO2) x (Al2O3) y gate dielectrics with different composition and permittivity by atomic layer deposition. A dielectric surface morphology dominated interface scattering carrier transport mechanism is demonstrated, and the effect of the dielectric polarization and the interface states on the carrier mobility is discovered in TFT devices gated by high quality dielectrics with negligible charge trap effect. Accordingly, an a-IGZO TFT gated by (HfO2)0.5(Al2O3)0.5 dielectric with the smoothest surface exhibits the best performance in terms of a preferable field-effect mobility of 18.35 cm2 Vâˆ'1 sâˆ'1, a small subthreshold swing of 0.105 V decadeâˆ'1, a high on/off current ratio of 4.6 Ă— 106, and excellent stability under positive bias stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flexible Cu-Ni traces with multiscale core–shell structures are generated by printing. • Relationship among formula, posttreatment, microstructure and properties is studied. • The formation mechanism of multiscale core–shell structures is clarified. • Aging behaviors and antioxidant mechanism of the Cu-Ni traces are investigated. Direct printing of flexible Cu traces is one of the most promising additive manufacturing technologies in advanced electronics because it is a cost-effective and environmentally friendly process. However, the low oxidation resistance of Cu is currently a critical issue for the preparation of high-performance metallic inks and the manufacturing of reliable printed traces. Herein, we propose a hybrid ink containing Cu/Ni complexes and Cu particles that can be directly printed onto polyimide substrates to generate high-performance Cu–Ni alloy traces by low-temperature preheating and intense pulsed-light irradiation. The nanoparticles in-situ formed by the decomposition of the complexes effectively bridge the interfaces among Cu particles, allowing the printed traces after subsequent intense pulsed-light irradiation to achieve a low resistivity of 29.4 μΩ·cm and excellent mechanical stability at a bending radius of 7 mm. Strikingly, the obtained Cu–Ni alloy traces achieve multiscale core–shell structures because of the heterogeneous nucleation and passivation of Ni, which enables the printed traces to maintain high conductivity and oxidation resistance even at 250 °C in the air, showing strong potential for use in advanced electronics manufacturing. [ABSTRACT FROM AUTHOR]

Abstract: We report one-step formation of the gate dielectric and conduction channel for enhancing the performance of organic field effect transistors (OFETs). The resulting OFET with the semiconductor/dielectric bi-layers spun in ambient conditions exhibits μ FET up to 1.6cm2/Vs and on–off ratio higher than 106, no additional treatment needed. Contact angle measurements and absorption spectra reveals that a well-defined semiconductor-top and dielectric-bottom film form after spin-coating the mixture of the two components, which is due to the surface induced self-organized phase separation. Compared to the single layer semiconductor film, the staggered film exhibits over 5 times higher mobility and nearly 90% reduced hysteresis in OFET. The higher performance is attributed to the simultaneous optimization in the dielectric interface and semiconductor crystallization. The approach is significant for the fabrication of low cost, easy processed and high performance OFETs. [Copyright &y& Elsevier]

Additive printing techniques have been widely investigated for fabricating multilayered electronic devices. In this work, a layer‐by‐layer printing strategy is developed to fabricate multilayered electronics including 3D conductive circuits and thin‐film transistors (TFTs) with low‐temperature catalyzed, solution‐processed SiO2 (LCSS) as the dielectric. Ultrafine, ultrasmooth LCSS films can be facilely formed at 90 °C on a wide variety of organic and inorganic substrates, offering a versatile platform to construct complex heterojunction structures with layer‐by‐layer fashion at microscale. The high‐resolution 3D conductive circuits formed with gold nanoparticles inside the LCSS dielectric demonstrate a high‐speed response to the transient voltage in less than 1 µs. The TFTs with semiconducting single‐wall carbon nanotubes can be operated with the accumulation mode at a low voltage of 1 V and exhibit average field‐effect mobility of 70 cm2 V−1 s−1, on/off ratio of 107, small average hysteresis of 0.1 V, and high yield up to 100% as well as long‐term stability, high negative‐gate bias stability, and good mechanical stability. Therefore, the layer‐by‐layer printing strategy with the LCSS film is promising to assemble large‐scale, high‐resolution, and high‐performance flexible electronics and to provide a fundamental understanding for correlating dielectric properties with device performance. [ABSTRACT FROM AUTHOR]

Three new solution‐processable organic semiconductors (1–3) are synthesized and characterized for p‐type organic field effect transistors (OFETs). The backbone of these small molecules is modified by expanding the central core conjugation from thienothiophene (TT) to dithienothiophene (DTT) and tetrathienoacene (TTA), which are end‐capped with soluble β‐substituted alkyl chains dithienothiophenes (DTTR) to generate DTTR‐TT (1), DTTR‐DTT (2), and DTTR‐TTA (3). The highest mobility of 0.016 cm2 V−1 s−1 is achieved using solution‐sheared DTTR‐TTA film due to the extended conjugated TTA core, which enhances the intermolecular interaction and generates an efficient percolation for the OFET channel. Solution blending of crystalline DTTR‐TT small molecules with oriented‐packing polymer dithienothiophene‐thioalkylbithiophene (PDTT‐SBT) polymer leads to significantly enhanced mobilities from 0.0009 up to 0.22 cm2 V−1 s−1, occurring at an optimized 30% DTTR‐TT composition in the blend. Hole mobility of 30% DTTR‐TT blend is 0.22 cm2 V−1 s−1 which is higher than pristine small molecule DTTR‐TT (0.0009 cm2 V−1 s−1) and polymer PDTT‐SBT (0.067 cm2 V−1 s−1), respectively. An efficient strategy to enhance the mobility of small molecule DTTR‐TT by blending with easily synthesizable PDTT‐SBT polymer is reported. [ABSTRACT FROM AUTHOR]

The electronic states of single crystalline (SC) rubrene were experimentally observed by photoelectron yield spectroscopy without the sample charging problem. The ionization energy (Is) in the SC phase was determined to be 4.85(±0.05) eV, which is reduced by 0.45 eV compared to that of the amorphous film. The changes in the electronic states during photo-oxidation reaction and under ambient air were also observed directly to reveal the further reduction in Is, which can be attributed to the generation of polar oxide molecules and reversible physisorption of H2O, respectively. [ABSTRACT FROM AUTHOR]

Joule's law opens a straightforward way to explore the operating mechanism of organic field-effect transistors, from the angle of inner transported heating. The microscopic dissipated power is calculated from the local conductivity and electric field, which solves the widespread difficulties in building a macroscopic model to determine the contact resistance. The result quantitatively discloses the correlation between the contact resistance and the charge transport properties covering energetic disorder, band-like and hopping transport as well as carrier mobility anisotropy. It turns out that in a staggered configuration with ideal Ohmic contact, the contact resistance is highly affected by the charge transport. [ABSTRACT FROM AUTHOR]

In this study, polymer‐based organic field‐effect transistors (OFETs) that exhibit alignment‐induced mobility enhancement, very small device‐to‐device variation, and high operational stability are successfully fabricated by a simple coating method of semiconductor solutions on highly hydrophobic nanogrooved surfaces. The highly hydrophobic nanogrooved surfaces (water contact angle >110°) are effective at inducing unidirectional alignment of polymer backbone structures with edge‐on orientation and are advantageous for realizing high operational stability because of their water‐repellent nature. The dewetting of the semiconductor solution is a critical problem in the thin film formation on highly hydrophobic surfaces. Dewetting during spin coating is suppressed by surrounding the hydrophobic regions with hydrophilic ones under appropriate designs. For the OFET array with an aligned terrace‐phase active layer of poly(2,5‐bis(3‐hexadecylthiophene‐2‐yl)thieno[3,2‐b]thiophene), the hole mobility in the saturation regime of 30 OFETs with channel current direction parallel to the nanogrooves is 0.513 ± 0.018 cm2 V−1 s−1, which is approximately double that of the OFETs without nanogrooves, and the intrinsic operational stability is comparable to the operational stability of amorphous‐silicon field‐effect transistors. In other words, alignment‐induced mobility enhancement and high operational stability are successfully achieved with very small device‐to‐device variation. This coating method should be a promising means of fabricating high‐performance OFETs. [ABSTRACT FROM AUTHOR]

A study of carrier transport in top-gate and bottom-contact TIPS-pentacene organic field-effect transistors (OFETs) based on mobility is presented. Among three mobilities extracted by different methods, the low-field mobility obtained by the Y function exhibits the best reliability and ease for use, whereas the widely applied field-effect mobility is not reliable, particularly in short-channel transistors and at low temperatures. A detailed study of contact transport reveals its strong impact on short-channel transistors, suggesting that a more intrinsic transport analysis is better implemented in relatively longer-channel devices. The observed temperature dependences of mobility are well explained by a transport model with Gaussian-like diffusivity band tails, different from diffusion in localized states band tails. This model explicitly interprets the non-zero constant mobility at low temperatures and clearly demonstrates the effects of disorder and hopping transport on temperature and carrier density dependences of mobility in organic transistors. [ABSTRACT FROM AUTHOR]

The rapid sintering of printable metal nanoparticle inks is vital for the industrial mass production of electronic devices. In this paper, we report a rapid laser annealing method for printed Ag nanoparticle-based inks. We also fabricate Ag circuits and organic thin-film transistors (OTFTs) on flexible plastic substrates through spontaneous patterning under deep ultraviolet (DUV) exposure. Compared to the conventional thermal annealing, laser annealing significantly reduces the processing time from 3600 to 10 s while preventing damage caused by excessive heat. The OTFT with laser-annealed Ag source/drain electrodes achieved good performance with saturated mobility of 1.68 cm $^{{2}}\cdot \text{V}^{-{1}}\cdot \text{s}^{-{1}}$ , high-reliability factor of 86.75%, and large saturated drain current resulting from the small channel resistance. This rapid laser annealing method is feasible for printing flexible electronics using metal nanoparticle-based inks in industrial mass production. [ABSTRACT FROM AUTHOR]

Abstract High-performance solution-processable organic semiconductors (OSCs) with wide bang gap (≥3.3eV) are highly required for fabricating transparent organic thin-film transistors (OTFTs) with the inexpensive and low-temperature printed technique. Herein, in this study, we reported the newly synthesized chrysene-based OSCs (di-CR-C 12 , mono-CR-C 12) with considerably large band gap of 3.70 eV, superior liquid crystallinity and solution-processed OTFTs mobility as high as 0.5 cm2/V. Such large band gap resulted in complete optical transparency of thin film in the visible-light region and good photostability. Highly ordered smectic E (SmE) phase of mono-CR-C 12 was the first reported case of the monoalkylated single core structure demonstrating advantageous capacity of CR backbone in stablizing Sm mesophase. Remarkably, high hole mobility exceeding 0.1 cm2/V in the bulk phase was determined by time-of-flight (TOF) technique intrinsically revealing their satisfactory carrier transport characteristics. Good solubility of mono-CR-C 12 enables solution-processed OTFTs with Au nanoparticles deposited at room-temperature and under ambient conditions, exhibiting good device performance with mobility up to 0.5 cm2/V. All results demonstrate that they are very promising candidates as active component for transparent electronics based on OTFTs. Graphical abstract Image 1 Highlights • In this study, High-performance solution-processable organic semiconductors (OSCs) with wide bang gap (≥3.3 eV) are highly required for fabricating transparent organic thin-film transistors (OTFTs) with the inexpensive and low-temperature printed technique. • Herein, in this study, we reported the newly synthesized chrysene-based OSCs (di-CR-C 12 , mono-CR-C 12) with considerably large band gap of 3.70 eV, superior liquid crystallinity and fully solution-processed organic thin-film transistors (OTFTs) mobility as high as 0.5 cm2/V. • Such large band gap resulted in complete optical transparency of thin film in the visible-light region and good photostability. • Highly ordered smectic E (SmE) phase of mono-CR-C 12 was the first reported case of the monoalkylated single core structure demonstrating advantageous capacity of CR backbone in stablizing Sm mesophase. • Remarkably, high hole mobility exceeding 0.1 cm2/V in the bulk phase of them was determined by time-of-flight (TOF) technique intrinsically revealing their satisfactory carrier transport characteristics. • Good solubility of mono-CR-C 12 enables solution-processed OTFTs with Au nanoparticles deposited at room-temperature and under ambient conditions, exhibiting good device performance with field-effect mobility up to 0.5 cm2/V. • All results demonstrate that they are very promising candidates as active component for transparent electronics based on OTFTs. [ABSTRACT FROM AUTHOR]

Printing device arrays of the non-volatile memory transistors is highly desired in the roll-to-roll manufacturing of integrated circuits. Here, we demonstrate the utilization of an insulating biomacromolecule of DNA in the printed transistor memory. A new DNA derivative was synthesized via an ion-exchange reaction in the aqueous solution. Homogeneous molecular orientation in DNA derivative was achieved through a solution process in butanol, which can be employed as the dielectric with a densely packed structure and a good insulating property. The engineered DNA derivative enables to fabricate integrated organic thin-film transistor (OTFT) memories on a large-area flexible substrate in ambient atmosphere. Combining the results of low-frequency dependence of capacitance and a retention time of more than 100 s, this solution-processed DNA-complex was revealed to be a ferroelectric-like dielectric. The printed memories exhibit hole mobility of 0.65 cm 2 V −1 s −1 and a large memory window up to 13 V, which is enough for a plenty of applications. Therefore, this approach is promising for printing large-scale flexible OTFT memories and for realizing various integrated electronics. [ABSTRACT FROM AUTHOR]

Microflow Manipulation by Velocity Field Gradient: Spontaneous Patterning of Silver Nanowires for Tailored Flexible Transparent Conductors (Adv. The resulting self-organized patterns are characterized by arbitrarily functional circuit design and precise AgNW fixation, which leads to the freeform transparent conductors with high performance. Directed self-assembly, flexible transparent heaters, patterning, silver nanowires, transparent conductors. [Extracted from the article]

Inspired by the silicide technology in manufacturing silicon devices and the ongoing lack of knowledge on post-metallization annealing in realizing oxide devices, we investigated post-contact annealing for solution-processed InGaZnO transistors. Low-temperature annealing in air is found to significantly improve device uniformity, reproducibility, and subthreshold charge transport. However, this method is highly dependent on the employed contact metal. Detailed examination of devices using Al, Au, and Cu reveals that the physics of a metal/semiconductor interface is vital to its post-anneal response, which results in distinct device characteristics. Our results provide clues to better understand oxide transistors and to optimize their performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Highly improve the n-type OFETs by transfer-printed Au electrodes. [•] Use Au electrode to obtain mobility similar to that using Ca and Al electrodes. [•] Transfer-printed p–n heterojunction by solution process for ambipolar OFETs. [•] Balanced hole–electron transport in coplanar, symmetric structure. [ABSTRACT FROM AUTHOR]

Abstract: We propose that solvent-vapor annealing is an efficient method for fabricating large [6,6]-phenyl C61 butyric acid methyl (PCBM) single crystals. The morphology and size of PCBM crystals are influenced by different substrates and annealing solvents. Hexagonal PCBM crystals >150 μm in size were obtained when crystallization was performed on bare SiO2 substrate under the saturated vapor of chloroform for annealing. The proposed method was also applied to a bi-component system, which led to the spontaneous formation of PCBM and dioctylbenzothienobenzothiophene single crystals. [Copyright &y& Elsevier]

Abstract: We control the growth of high-quality organic semiconducting crystals in the aim of transistor application. By finely tuning the processing parameters, both isolated crystals showing characteristic facet angles and irregular-shaped, thin crystalline domains are obtained in large sizes (>400μm). Structural investigations indicate that the various shapes of crystals are in the same crystal structure, and reveal that the irregular-shaped crystalline domains are composed by terrace of molecularly flat regions, which can be up to hundreds of microns in size. When applied in field-effect transistors, the thin crystalline domains exhibit the best performance showing μ FET up to 4.4cm2/Vs. This is an order of magnitude higher than that of the transistors made from as-spun films and thick crystals. The approach well demonstrates the importance of fine control of crystal formation and can be generally used for getting organic crystal transistors. [Copyright &y& Elsevier]

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. [ABSTRACT FROM PUBLISHER]

Abstract: A study of the contact resistance (R sd) in pentacene-based double-gate transistors is presented. In top-contact transistors, as the negative bias of the additional top-gate bias is increased, R sd decreases by over five orders of magnitude for small bottom-gate voltages. In bottom-contact transistors, R sd is reduced by about ten times for all bias values, implying improved charge transport in all operating regimes. The different tunability of R sd in top/bottom-contact transistors is attributed to different charge injection modulation by the coplanar/staggered top gate. Therefore, double-gate architecture offers a novel and effective approach to limit R sd and its relevant impacts on organic transistor. [Copyright &y& Elsevier]

A correction to the article "Direct observation of the electronic states of single crystalline rubrene under ambient condition by photoelectron yield spectroscopy" that was published in the 2008 issue is presented.

Abstract: Large surface roughness is a major obstacle for electronic systems fabricated on paper substrates. Here, a mixture solution of organic semiconductor and polymer dielectric was spin-coated on paper substrate with a patterned wettability. This spin-coating process produced organic crystals and a very smooth semiconductor/dielectric interface with a low trap density in well-confined patterns. Despite the large roughness of the paper substrate, the fabricated transistor arrays exhibited high performance with a field-effect mobility reaching 1.3cm2/Vs and an on/off ratio of 108. The presented results offer a simple fabrication method for the current rapidly developing technology of paper electronics. [Copyright &y& Elsevier]

Abstract: Solution-processed organic crystals are important in field-effect transistors because of their highly ordered molecular packing and ease of device fabrication. For practical applications, the patterning of organic crystal transistor arrays is critical. However, uniformity, which concerns the variation in electrical performance among devices fabricated simultaneously on the same substrate, is a common consideration in the commercial applications of the solution-processed organic crystal transistor arrays. Here, a simple approach for fabricating field-effect transistor arrays based on organic plate-like crystals is reported. Through this method, a direct spin-coating process from a mixture solution of organic semiconductor and polymer dielectric can produce organic plate-like crystals. The grain size of the crystals is observed to be hundreds of micrometers. By controlling the concentrations of the active materials, the transistor arrays exhibit high uniformity and good device performance. The results presented in this work promise that this approach is a comparable technology to hydrogenated amorphous silicon-based FETs and is a great candidate for practical applications in electronic devices. [Copyright &y& Elsevier]

Despite a large steric bulk of C60, a molecular graphene with a covalently linked C60 pendant [hexabenzocoronene (HBC)-C60; 1] self-assembles into a coaxial nanotube whose wall consists of a graphite-like π-stacked HBC array, whereas the nanotube surface is fully covered by a molecular layer of clustering C60. Because of this explicit coaxial configuration, the nanotube exhibits an ambipolar character in the field-effect transistor output [hole mobility (μh) = 9.7 × 10-7 cm² V-1 s-1; electron mobility (μe) = 1.1 × 10-5 cm² V-1 s-1) and displays a photovoltaic response upon light illumination. Successful coassembly of 1 and an HBC derivative without C60 (2) allows for tailoring the p/n heterojunction in the nanotube, so that its ambipolar carrier transport property can be optimized for enhancing the open-circuit voltage in the photovoltaic output. As evaluated by an electrodeless method called flash-photolysis time-resolved microwave conductivity technique, the intratubular hole mobility (2.0 cm² V-1 s-1) of a coassembled nanotube containing 10 mol % of HBC-C60 (1) is as large as the intersheet mobility in graphite. The homotropic nanotube of 2 blended with a soluble C60 derivative [(6,6)-phenyl C61 butyric acid methyl ester] displayed a photovoltaic response with a much different composition dependency, where the largest open-circuit voltage attained was obviously lower than that realized by the coassembly of 1 and 2. [ABSTRACT FROM AUTHOR]

Back Cover In article number 2100263, Liu, Zhao, Minari, and co‐workers report a layer‐by‐layer printing strategy for high‐performance flexible electronics, including 3D circuits and thin‐film transistors (TFTs). Low‐temperature catalyzed solution‐processed SiO2 (LCSS) was developed as the interlayer insulating medium which enables fabrication of printed TFTs with a field‐effect mobility of 70 cm2 V−1 s−1 at operation voltages below 1 V. [ABSTRACT FROM AUTHOR]