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1.
Organic Electronics: Control of Ambipolar and Unipolar Transport in Organic Transistors by Selective Inkjet‐Printed Chemical Doping for High Performance Complementary Circuits (Adv. Funct. Mater. 40/2014) 
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下载免费PDF全文 Dongyoon Khim Kang‐Jun Baeg Mario Caironi Chuan Liu Yong Xu Dong‐Yu Kim Yong‐Young Noh 《Advanced functional materials》2014,24(40):6245-6245
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Björn Lüssem Hans Kleemann Daniel Kasemann Fabian Ventsch Karl Leo 《Advanced functional materials》2014,24(7):1011-1016
The realization and performance of a novel organic field‐effect transistor—the organic junction field‐effect transistor (JFET)—is discussed. The transistors are based on the modulation of the thickness of a depletion layer in an organic pin junction with varying gate potential. Based on numerical modeling, suitable layer thicknesses and doping concentrations are identified. Experimentally, organic JFETs are realized and it is shown that the devices clearly exhibit amplification. Changes in the electrical characteristics due to a variation of the intrinsic and the p‐doped layer thickness are rationalized by the numerical model, giving further proof to the proposed operational mechanism. 相似文献
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Xiaofeng Wu Ruofei Jia Jiansheng Jie Mi Zhang Jing Pan Xiujuan Zhang Xiaohong Zhang 《Advanced functional materials》2019,29(51)
Organic field‐effect transistors (OFETs) often deviate from ideal behaviors in air, which masks their intrinsic properties and thus significantly impedes their practical applications. A key issue of how the presence of air affects the ideality of OFETs has not yet been fully understood. It is revealed that air atmosphere may exert a double‐edged sword effect on the active semiconductor layer when determining the ideality of OFETs fabricated from p‐type crystalline organic semiconductors. Upon exposing the as‐fabricated device to air, water and oxygen mainly function as efficient p‐type dopants for the active layer in the contact regions, enhancing charge carrier injection and consequently improving device ideality. Nevertheless, as the exposure time increases, the trapping centers for the injected minority charge carriers appear in the channel region, leading to degradation of device ideality. Inspired by the double‐edged sword behavior of air, a near‐ideal OFET is achieved by ingeniously utilizing the doping/positive effect and eliminating the trapping/negative effect. The effect of air on the ideality of p‐type OFETs is clarified, which not only illuminates some common observations of OFETs in air but also offers useful guidance for the construction of high‐performance ideal OFETs. 相似文献
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Contact resistance has long been a major problem in organic transistors. The potential advantages of having such a resistance in novel organic field‐effect complementary inverters are demonstrated by means of finite‐element simulation. A systematic introduction of the charge‐injection barrier leads to a remarkable enhancement in the voltage transfer curve. Quantitatively, the maximum gain increases from 8.9 to 50 by increasing the barrier from 0 to 0.5 eV, at a dielectric thickness of 600 nm and a supply voltage of 5 V. This observation is elucidated by the fundamental transistor parameters and by the carrier distribution inside the semiconductors. These results suggest that the established paradigm of device engineering may have to be reconsidered when designing specific circuit applications. 相似文献
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Matthew Waldrip Oana D. Jurchescu David J. Gundlach Emily G. Bittle 《Advanced functional materials》2020,30(20)
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. 相似文献
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Kumar A. Singh Tomasz Young Richard D. McCullough Tomasz Kowalewski Lisa M. Porter 《Advanced functional materials》2010,20(14):2216-2221
The planarization of bottom‐contact organic field‐effect transistors (OFETs) resulting in dramatic improvement in the nanomorphology and an associated enhancement in charge injection and transport is reported. Planar OFETs based on regioregular poly(3‐hexylthiophene) (rr‐P3HT) are fabricated wherein the Au bottom‐contacts are recessed completely in the gate‐dielectric. Normal OFETs having a conventional bottom‐contact configuration with 50‐nm‐high contacts are used for comparison purpose. A modified solvent‐assisted drop‐casting process is utilized to form extremely thin rr‐P3HT films. This process is critical for direct visualization of the effect of planarization on the polymer morphology. Atomic force micrographs (AFM) show that in a normal OFET the step between the surface of the contacts and the gate dielectric disrupts the self‐assembly of the rr‐P3HT film, resulting in poor morphology at the contact edges. The planarization of contacts results in notable improvement of the nanomorphology of rr‐P3HT, resulting in lower resistance to charge injection. However, an improvement in field‐effect mobility is observed only at short channel lengths. AFM shows the presence of well‐ordered nanofibrils extending over short channel lengths. At longer channel lengths the presence of grain boundaries significantly minimizes the effect of improvement in contact geometry as the charge transport becomes channel‐limited. 相似文献
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Dang Xuan Long Kang‐Jun Baeg Yong Xu Seok‐Ju Kang Myung‐Gil Kim Geon‐Woong Lee Yong‐Young Noh 《Advanced functional materials》2014,24(41):6484-6491
In this paper, a technique using mixed transition‐metal oxides as contact interlayers to modulate both the electron‐ and hole‐injections in ambipolar organic field‐effect transistors (OFETs) is presented. The cesium carbonate (Cs2CO3) and vanadium pentoixide (V2O5) are found to greatly and independently improve the charge injection properties for electrons and holes in the ambipolar OFETs using organic semiconductor of diketopyrrolopyrrolethieno[3,2‐b]thiophene copolymer (DPPT‐TT) and contact electrodes of molybdenum (Mo). When Cs2CO3 and V2O5 are blended at various mixing ratios, they are observed to very finely and constantly regulate the Mo's work function from ?4.2 eV to ?4.8 eV, leading to high electron‐ and hole‐mobilities as high as 2.6 and 2.98 cm2 V?1 s?1, respectively. The most remarkable finding is that the device characteristics and device performance can be gradually controlled by adjusting the composition of mixed‐oxide interlayers, which is highly desired for such applications as complementary circuitry that requires well matched n‐channel and p‐channel device operations. Therefore, such simple interface engineering in conjunction with utilization of ambipolar semiconductors can truly enable the promising low‐cost and soft organic electronics for extensive applications. 相似文献
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Gitish K. Dutta A‐Reum Han Junghoon Lee Yiho Kim Joon Hak Oh Changduk Yang 《Advanced functional materials》2013,23(42):5317-5325
Systematic creation of polymeric semiconductors from novel building blocks is critical for improving charge transport properties in organic field‐effect transistors (OFETs). A series of ultralow‐bandgap polymers containing thienoisoindigo (TIIG) as a thiophene analogue of isoindigo (IIG) is synthesized. The UV‐Vis absorptions of the TIIG‐based polymers ( PTIIG‐T , PTIIG‐Se , and PTIIG‐DT ) exhibit broad bands covering the visible to near‐infrared range of up to 1600 nm. All the polymers exhibit unipolar p‐channel operations with regard to gold contacts. PTIIG‐DT with centrosymmetric donor exhibits a maximum mobility of 0.20 cm2 V?1 s?1 under gold contacts, which is higher than those of the other polymers containing axisymmetric donors. Intriguingly, OFETs fabricated with aluminum electrodes show ambipolar charge transport with hole and electron mobilities of up to 0.28 ( PTIIG‐DT ) and 0.03 ( PTIIG‐T ) cm2 V?1 s?1, respectively. This is a record value for the hitherto reported TIIG‐based OFETs. The finding demonstrates that TIIG‐based polymers can potentially function as either unipolar or ambipolar semiconductors without reliance on the degree of electron affinity of the co‐monomers. 相似文献
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Wei‐Ling Seah Cindy G. Tang Rui‐Qi Png Venu Keerthi Chao Zhao Han Guo Jin‐Guo Yang Mi Zhou Peter K. H. Ho Lay‐Lay Chua 《Advanced functional materials》2017,27(18)
Contact resistance limits the performance of organic field‐effect transistors, especially those based on high‐mobility semiconductors. Despite intensive research, the nature of this phenomenon is not well understood and mitigation strategies are largely limited to complex schemes often involving co‐evaporated doped interlayers. Here, this study shows that solution self‐assembly of a polyelectrolyte monolayer on a metal electrode can induce carrier doping at the contact of an organic semiconductor overlayer, which can be augmented by dopant ion‐exchange in the monolayer, to provide ohmic contacts for both p‐ and n‐type organic field‐effect transistors. The resultant 2D‐doped profile at the semiconductor interface is furthermore self‐aligned to the contact and stabilized against counterion migration. This study shows that Coulomb potential disordering by the polyelectrolyte shifts the semiconductor density‐of‐states into the gap to promote extrinsic doping and cascade carrier injection. Contact resistivities of the order of 0.1–1 Ω cm2 or less have been attained. This will likely also provide a platform for ohmic injection into other advanced semiconductors, including 2D and other nanomaterials. 相似文献
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A‐Reum Han Gitish K. Dutta Junghoon Lee Hae Rang Lee Sang Myeon Lee Hyungju Ahn Tae Joo Shin Joon Hak Oh Changduk Yang 《Advanced functional materials》2015,25(2):247-254
Based on the integrated consideration and engineering of both conjugated backbones and flexible side chains, solution‐processable polymeric semiconductors consisting of a diketopyrrolopyrrole (DPP) backbone and a finely modulated branching side chain (ε‐branched chain) are reported. The subtle change in the branching point from the backbone alters the π?π stacking and the lamellar distances between polymer backbones, which has a significant influence on the charge‐transport properties and in turn the performances of field‐effect transistors (FETs). In addition to their excellent electron mobilities (up to 2.25 cm2 V?1 s?1), ultra‐high hole mobilities (up to 12.25 cm2 V?1 s?1) with an on/off ratio (Ion/Ioff) of at least 106 are achieved in the FETs fabricated using the polymers. The developed polymers exhibit extraordinarily high electrical performance with both hole and electron mobilities superior to that of unipolar amorphous silicon. 相似文献
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Peter Darmawan Takeo Minari Yong Xu Song‐Lin Li Haisheng Song Meiyin Chan Kazuhito Tsukagoshi 《Advanced functional materials》2012,22(21):4577-4583
A low contact resistance achieved on top‐gated organic field‐effect transistors by using coplanar and pseudo‐staggered device architectures, as well as the introduction of a dopant layer, is reported. The top‐gated structure effectively minimizes the access resistance from the contact to the channel region and the charge‐injection barrier is suppressed by doping of iron(III)trichloride at the metal/organic semiconductor interface. Compared with conventional bottom‐gated staggered devices, a remarkably low contact resistance of 0.1–0.2 kΩ cm is extracted from the top‐gated devices by the modified transfer line method. The top‐gated devices using thienoacene compound as a semiconductor exhibit a high average field‐effect mobility of 5.5–5.7 cm2 V?1 s?1 and an acceptable subthreshold swing of 0.23–0.24 V dec?1 without degradation in the on/off ratio of ≈109. Based on these experimental achievements, an optimal device structure for a high‐performance organic transistor is proposed. 相似文献
16.
Ke Zhang Naresh B. Kotadiya Xiao‐Ye Wang Gert‐Jan A. H. Wetzelaer Tomasz Marszalek Wojciech Pisula Paul W. M. Blom 《Advanced Electronic Materials》2020,6(6)
Efficient charge‐carrier injection is a critical requirement for high‐performance organic electronic devices, such as light‐emitting diodes, solar cells, and field‐effect transistors. In this work, a significantly improved charge‐carrier injection from high work‐function metal‐oxide electrodes in organic field effect transistors (OFETs) is demonstrated for amorphous organic semiconductors (OSCs) by using organic interlayers with a high ionization energy (IE). Molybdenum oxide (MoO3) exhibits limited injection into amorphous 2,2′,7,7′‐tetrakis(N,N‐diphenylamino)‐9,9‐spirobifluorene (Spiro‐TAD) and tris(4‐carbazoyl‐9‐ylphenyl)amine (TCTA) active layers, resulting in high contact resistance and threshold voltage. By inserting an interlayer of a few nanometers thick with high IE between the MoO3 electrode and the amorphous OSC films, the Spiro‐TAD and TCTA OFETs show a substantial enhancement in hole current, subthreshold swing, and effective charge carrier mobility due to the decreased contact resistance. However, for discontinuous interlayers formed on distinct grain domains as in the case of polycrystalline 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) films, the effect of the interlayer reduces. These results demonstrate that the utilization of smooth interlayers with IE higher than the semiconductor is a general approach to elevate the hole injection into amorphous OSCs with high IE in OFETs. 相似文献
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The mismatch of energy alignment of low‐cost metals with organic semiconductors requires interfacial modification of the electrodes in organic field‐effect transistors (OFETs). However, traditional methods involve chemicals and operations that introduce potential contaminations or damages to the device, which deteriorate the device performance. Here, an inner‐evaporator modification method using ultrathin polyporphyrin film (≈1.1 nm) as the interlayer between semiconductor and Ag or Cu electrode is developed. Both the modification and device fabrication are processed simultaneously in the high‐vacuum environment of the thermal evaporator. After the contamination‐free modification, the contact resistance decreases by 2–3 orders of magnitude, and the field‐effect mobility of pentacene is one of the highest values among pentacene thin‐film bottom‐contact OFETs based on modified Ag/Cu electrodes, comparable to that of modified Au electrodes. Owing to its simplicity, efficiency in improving device performance, and compatibility with OFET fabrication process, this method has great potential for application in future organic electronics with low‐cost metal electrodes. 相似文献
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Wee Chong Tan Lin Wang Xuewei Feng Li Chen Li Huang Xin Huang Kah‐Wee Ang 《Advanced Electronic Materials》2019,5(2)
The rediscovery of graphene in the recent past has propelled the rapid development of exfoliation and other thin layer processing techniques, leading to a renewed interest in black phosphorus (BP). Since 2014, BP has been extensively studied due to its superior electronic, photonic, and mechanical properties. In addition, the unique intrinsic anisotropic characteristics resulting from its puckered structure can be utilized for designing new functional devices. In retrospect, significant efforts have been directed toward the synthesis, basic understanding, and applications of BP in the fields of nanoelectronics, ultrafast optics, nanophotonics, and optoelectronics. Here, the recent development of BP‐based devices, such as nanoribbon field‐effect transistors, complementary logic circuits, memory devices, and the progress made in meeting the challenges associated with contact resistance, in‐plane anisotropy, and advanced gate stack, are reviewed. Finally, the prospects of 2D materials in meeting the International Technology Roadmap for Semiconductor requirements for the year 2030 are discussed. 相似文献
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Ambipolar charge transport in a solution‐processed small molecule 4,7‐bis{2‐[2,5‐bis(2‐ethylhexyl)‐3‐(5‐hexyl‐2,2′:5′,2″‐terthiophene‐5″‐yl)‐pyrrolo[3,4‐c]pyrrolo‐1,4‐dione‐6‐yl]‐thiophene‐5‐yl}‐2,1,3‐benzothiadiazole (BTDPP2) transistor has been investigated and shows a balanced field‐effect mobility of electrons and holes of up to ～10?2 cm2 V?1 s?1. Using low‐work‐function top electrodes such as Ba, the electron injection barrier is largely reduced. The observed ambipolar transport can be enhanced over one order of magnitude compared to devices using Al or Au electrodes. The field‐effect mobility increases upon thermal annealing at 150 °C due to the formation of large crystalline domains, as shown by atomic force microscopy and X‐ray diffraction. Organic inverter circuits based on BTDPP2 ambipolar transistors display a gain of over 25. 相似文献
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Chin‐Sheng Pang Terry Y. T. Hung Ava Khosravi Rafik Addou Qingxiao Wang Moon J. Kim Robert M. Wallace Zhihong Chen 《Advanced Electronic Materials》2020,6(8)
2D transitional metal dichalcogenide (TMD) field‐effect transistors are promising candidates for future electronic applications, owing to their potential for ultimate device scaling. However, it is acknowledged that substantial contact resistance associated with the contact‐TMD interface has impeded device performance to a large extent. It has been discovered that O2 plasma treatment can convert WSe2 into WO3−x and substantially improve contact resistances of p‐type WSe2 devices by strong doping induced thinner depletion width. In this paper, temperature dependence of this conversion is studied, demonstrating an oxidation process with a precise monolayer control at room temperature and multilayer conversion at elevated temperatures. Furthermore, lateral oxidation of WSe2 underneath contact revealed by high‐resolution scanning transmission electron microscope leads to potential unpinning of the metal Fermi level and Schottky barrier lowering, resulting in lower contact resistances. The p‐doping effect is attributed to the high electron affinity of the WO3−x layer on top of the remaining WSe2 channel, and the doping level is dependent on the WO3−x thickness that is controlled by the temperature. Comprehensive materials and electrical characterizations are presented, with a low contact resistance of ≈528 Ω μm and record high on‐state current of 320 μA μm−1 at −1 V bias being reported. 相似文献
