Due to their advantages of low cost, flexibility, ease of manufacture and biocompatibility, organic thin film transistor (OTFT) hold great commercial potential. Specifically, there are two types of ...OTFT, OFET and OECT, which are widely used in the field of flexible biological sensors and have great ability for glucose and DNA detection of diabetes. In this paper, we describe the working principles of OFET and OECT, and compare the differences between them. Some examples are given and clarified, including the materials, fabrication and chemical reactions. There is still a lot of space to be explored in OTFT for other biomarker sensing applications. With the emergence of new materials and fabrication techniques, OTFT-based biosensor would be more widely used in diagnostic equipment to improve patient outcomes.
2D tin‐based perovskites have gained considerable attention for use in diverse optoelectronic applications, such as solar cells, lasers, and thin‐film transistors (TFTs), owing to their good ...stability and optoelectronic properties. However, their intrinsic charge‐transport properties are limited, and the insulating bulky organic ligands hinder the achievement of high‐mobility electronics. Blending 3D counterparts into 2D perovskites to form 2D/3D hybrid structures is a synergistic approach that combine the high mobility and stability of 3D and 2D perovskites, respectively. In this study, reliable p‐channel 2D/3D tin‐based hybrid perovskite TFTs comprising 3D formamidinium tin iodide (FASnI3) and 2D fluorinated 4‐fluoro‐phenethylammonium tin iodide ((4‐FPEA)2SnI4) are reported. The optimized FPEA‐incorporated TFTs show a high hole mobility of 12 cm2 V−1 s−1, an on/off current ratio of over 108, and a subthreshold swing of 0.09 V dec−1 with negligible hysteresis. This excellent p‐type characteristic is compatible with n‐type metal‐oxide TFT for constructing complementary electronics. Two procedures of antisolvent engineering and device patterning are further proposed to address the key concern of low‐performance reproducibility of perovskite TFTs. This study provides an alternative A‐cation engineering method for achieving high‐performance and reliable tin‐halide perovskite electronics.
A reliable p‐channel 2D/3D tin‐based hybrid perovskite thin‐film transistors (TFTs) comprising 3D formamidinium tin iodide (FASnI3) and 2D fluorinated 4‐fluoro‐phenethylammonium tin iodide ((4‐FPEA)2SnI4) are reported. The optimized FPEA‐incorporated TFTs show a high hole mobility of 12 cm2 V−1 s−1, an on/off current ratio of over 108, and a subthreshold swing of 0.09 V dec−1 with negligible hysteresis.
Amorphous oxide semiconductors (AOSs) have been commercialized since 2012 as thin‐film transistor (TFT) backplanes in flat‐panel displays. This review first provides a brief history and current ...status of AOS technology, and then introduces electronic defects in AOSs reported to date that are critically important for understanding and controlling the instability of TFTs that is the most serious issue in the development of the AOS technology. In particular, it is important to know that many AOS defects are related to oxygen and hydrogen impurities, though oxygen is the major constituent of AOS and hydrogen is not intentionally incorporated. Instability issues and their underlying mechanisms are also discussed in relation to these defects.
Amorphous oxide semiconductors are currently employed in several flat‐panel displays, including large‐sized organic light‐emitting diode televisions. This paper reviews the defects in AOSs reported to date as well as provides a brief history and current status of AOS technology. TFT instability issues, their underling mechanisms, and optimum fabrication conditions are discussed in relation to these defects.
Paper-based pentacene organic thin-film transistors (OTFTs) with spin-coated gelatin (G) stacked gate dielectric layers, the Au/pentacene/G/G matrix-embedded iron (FeG)/Al/paper structure, were ...fabricated. The proposed composite-stacked bio-dielectric layer can be implemented using solutions with the degradable biomaterials. These materials enable a large-area printing of use-and-throw devices. Control devices (Au/pentacene/G/Al and Au/pentacene/FeG/Al structure) were also fabricated for comparison. High-performance paper-based OTFT constructed from the stacked gate dielectric layer exhibited a carrier mobility of 8 cm 2 /Vs, an ON/OFF current ratio of approximately 10 3 , a subthreshold swing of 0.6 V/decade, and a threshold voltage of -1.4 V. These results are compatible to those OTFTs fabricated on other substrates. Therefore, the emerging biomaterial-based transistors on paper substrates may help in developing low-cost, environment-friendly devices.
Organic semiconductors have sparked interest as flexible, solution processable, and chemically tunable electronic materials. Improvements in charge carrier mobility put organic semiconductors in a ...competitive position for incorporation in a variety of (opto‐)electronic applications. One example is the organic field‐effect transistor (OFET), which is the fundamental building block of many applications based on organic semiconductors. While the semiconductor performance improvements opened up the possibilities for applying organic materials as active components in fast switching electrical devices, the ability to make good electrical contact hinders further development of deployable electronics. Additionally, inefficient contacts represent serious bottlenecks in identifying new electronic materials by inhibiting access to their intrinsic properties or providing misleading information. Recent work focused on the relationships of contact resistance with device architecture, applied voltage, metal and dielectric interfaces, has led to a steady reduction in contact resistance in OFETs. While impressive progress was made, contact resistance is still above the limits necessary to drive devices at the speed required for many active electronic components. Here, the origins of contact resistance and recent improvement in organic transistors are presented, with emphasis on the electric field and geometric considerations of charge injection in OFETs.
The charge injection in organic field‐effect transistors (OFETs) is reviewed here, with emphasis on the interplay between device performance (beyond mobility) and contact resistance. The charge injection mechanisms in organic semiconductors in relation to OFET operation are summarized, and an overview of measurements for evaluation of contact resistance is provided along with recent progress in contact design, a historical overview, and future perspectives.
A stack passivation by spray pyrolysis is demonstrated for high performance and stable amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) thin‐film transistors (TFTs). The device performances and ...stabilities of a‐IGZO TFTs are compared with single zirconium‐aluminium‐oxide (ZAO), aluminium oxide (Al2O3), and stack ZAO/Al2O3 and Al2O3/ZAO passivation layers. The a‐IGZO TFTs with Al2O3/ZAO stack exhibit high performance and excellent stabilities under electrical, thermal, and environmental tests with negligible threshold voltage shift. The origin of the device performances and improved stabilities are analyzed using X‐ray photoelectron spectroscopy and high‐resolution transmission electron microscopy analyses. It is found that the Zr elements diffuse into the a‐IGZO channel when ZAO is directly deposited on the a‐IGZO, resulting in the deterioration of the device performance. It is also found that the Al2O3 single layer on top of the a‐IGZO cannot protect the back‐channel from moisture diffusion. But a thin Al2O3 layer on top of the TFTs can protect the diffusion of Zr elements from ZAO into the a‐IGZO channel and enhances the performance and stabilities. Therefore, the low cost, Al2O3/ZAO stack by spray pyrolysis on the sputtered a‐IGZO can be an excellent passivation for highly stable metal‐oxide TFTs.
A high‐quality passivation (PA) layer is demonstrated with low‐cost spray pyrolysis technique for highly stable amorphous indium‑gallium‑zinc‑oxide thin‐film transistors (TFTs). The TFTs with a stack aluminium oxide/zirconium‐aluminium oxide PA layer exhibit the negligible threshold voltage shift under gate bias temperature stress and also after the humidity exposure (85%) at 85 °C.
With a growing international trend of Cannabis legalization, there is a present need for on‐the‐spot, low cost, and rapid detection of cannabinoids. Here, relationships between thin‐films of ...phthalocyanines (Pcs) with a variety of central, peripheral, and axial substituents and their response to the cannabinoid Δ9‐tetrahydrocannabinol (THC), with and without a cannabinoid‐sensitive chromophore (Fast Blue BB) are investigated through organic thin‐film transistor (OTFT) performance. X‐ray diffraction and UV–vis absorption spectroscopy measurements demonstrate significantly altered film morphologies and the formation of new crystal orientations in response to analytes, which are corroborated by scanning electron microscopy. Electron paramagnetic resonance further corroborates shifting crystal structures in response to THC and also reveals the formation and promotion of Pc radical species through THC‐metal coordination. With exposure to THC, aluminum chloride Pc generates the largest physical film changes as well as the largest changes in OTFT performance. These findings suggest that the semiconductor thin‐film morphologies in Pc‐based OTFT sensors are not static in the presence of analytes and that the sensing response is driven both by strong analyte‐Pc coordination and bulk film restructuring to accommodate these interactions.
Phthalocyanine (Pc) thin films morphology will rearrange in the presence of Δ9‐tetrahydrocannabinol and a cannabinoid‐sensitive chromophore (Fast Blue BB). Variations in Pc center atoms and peripheral Pc substitutions provide unique Pc–analyte interactions, further tuning analyte induced film recrystallization: a change that can be detected electrically when incorporated into organic thin‐film transistors.
Bis(thiophen‐2‐yl)‐diketopyrrolopyrrole (DPP) dyes bearing various alkyl substituents at the amide positions (n‐butyl, n‐pentyl, n‐hexyl, n‐heptyl, n‐octyl, 2‐ethylhexyl) and chlorine (Cl), bromine ...(Br), or cyano (CN) substituents at the thiophene positions have been synthesized and investigated with regard to their molecular and semiconducting properties. Intense absorption, strong fluorescence, and reversible oxidation and reduction processes are common to all of these dyes. Their characterization as organic semiconductors in vacuum‐processed thin‐film transistors reveals p‐channel operation with field‐effect mobilities ranging from 0.01 to 0.7 cm2 V−1 s−1. The highest mobility is found for the DPP dyes bearing the 2‐ethylhexyl substituents, which is surprising, considering that as a result of the chiral substituents, this material is a mixture of (R,R), (S,S), and (R,S) stereoisomers. The high carrier mobility in the films of the DPPs bearing stereoisomerically inhomogeneous ethylhexyl groups is rationalized here by single‐crystal X‐ray diffraction (XRD) analysis in combination with XRD and atomic force microscopy studies on thin films, which reveal the presence of slightly different 2D layer arrangements for the n‐alkyl and the 2‐ethylhexyl derivatives. For the cyano‐substituted DPPs possessing the lowest LUMO levels, ambipolar transport characteristics are observed.
Twenty‐four diketopyrrolopyrrole dyes with branched and linear solubilizing alkyl chains and electron‐withdrawing substituents at the aromatic core are investigated as the semiconductor in organic thin‐film transistors. Remarkably, layers of stereoisomeric mixtures of the 2‐ethylhexyl‐substituted derivatives outperform the devices of dyes with n‐alkyl chains with carrier mobilities as high as 0.7 cm2 V−1 s−1.
By combining two kinds of solution‐processable two‐dimensional materials, a flexible transistor array is fabricated in which MoS2 thin film is used as the active channel and reduced graphene oxide ...(rGO) film is used as the drain and source electrodes. The simple device configuration and the 1.5 mm‐long MoS2 channel ensure highly reproducible device fabrication and operation. This flexible transistor array can be used as a highly sensitive gas sensor with excellent reproducibility. Compared to using rGO thin film as the active channel, this new gas sensor exhibits much higher sensitivity. Moreover, functionalization of the MoS2 thin film with Pt nanoparticles further increases the sensitivity by up to ∼3 times. The successful incorporation of a MoS2 thin‐film into the electronic sensor promises its potential application in various electronic devices.
By combining two kinds of solution‐processable 2D materials, a flexible transistor array is fabricated in which a MoS2 thin film is used as the active channel and a reduced graphene oxide (rGO) film is used as the drain and source electrodes. This flexible transistor array can be used as a highly sensitive gas sensor with excellent reproducibility. Compared to using rGO thin film as the active channel, this new gas sensor exhibits much higher sensitivity. Moreover, functionalization of the MoS2 thin film with Pt nanoparticles further increases the sensitivity by up to ∼3 times.
A series of thienoisoindigo (TIG)‐based conjugated polymers (CPs) with high molecular weights are synthesized by direct arylation polycondensation (DArP) by using TIG derivatives as CBr monomer and ...multi‐halogenated thiophene derivatives, i.e., (E)–1,2‐bis(3,4‐difluorothien‐2‐yl)ethene (4FTVT), (E)–1,2‐bis(3,4‐dichlorothien‐2‐yl)ethene (4ClTVT), 3,3',4,4'‐tetrafluoro‐2,2'‐bithiophene (4FBT), and 3,3',4,4'‐tetrachloro‐2,2'‐bithiophene (4ClBT), as CH monomers. Density functional theory (DFT) calculations reveal the high selectivity between α‐CH bonds in 4FTVT, 4ClTVT, 4FBT, and 4ClBT and β‐CH bonds in TIG CBr monomer. All four resulting CPs exhibit low optical bandgaps of ca. 1.20 eV and ambipolar transport characteristics with both electron and hole mobility above 0.1 cm2 V−1 s−1 as elaborated with organic thin‐film transistors (OTFTs). The polymer TIG‐4FTVT delivers the best device performance. With this polymer, n‐channel OTFTs with electron mobility up to 1.67 cm2 V−1 s−1 and p‐channel OTFTs with hole mobility up to 0.62 cm2 V−1 s−1 are fabricated by modifying source/drain electrodes with polyethylenimine ethoxylated (PEIE) and MoO3, respectively, to selectively inject electrons and holes.
High molecular weight thienoisoindigo (TIG) ‐ based ambipolar conjugated polymers with electron mobility up to 1.67 cm2 V−1 s−1 and hole mobility up to 0.62 cm2 V−1 s−1 are synthesized by direct arylation polycondensation with TIG derivative as C–Br monomer and multi‐halogenated thiophene derivatives as C–H monomers.
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