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Journal ArticleDOI

Study of electrical performance and stability of solution-processed n-channel organic field-effect transistors

02 Sep 2009-Journal of Applied Physics (American Institute of Physics)-Vol. 106, Iss: 5, pp 054504
TL;DR: In this paper, a solution processed n-channel organic field effect transistors based on [6,6]-phenyl C61 butyric acid methyl ester with high mobility and low contact resistance are reported.
Abstract: Solution processed n-channel organic field-effect transistors based on [6,6]-phenyl C61 butyric acid methyl ester with high mobility and low contact resistance are reported. Ca, Au, or Ca capped with Au (Ca/Au) was used as the top source/drain electrodes. The devices with Ca electrodes exhibit excellent n-channel behavior with electron mobility values of 0.12 cm2/V s, low threshold voltages (∼2.2 V), high current on/off ratios (105–106) and subthreshold slopes of 0.7 V/decade. By varying the channel lengths (25–200 μm) in devices with different metal/semiconductor interfaces, the effect of channel length scaling on mobility is studied and the contact resistance is extracted. The width-normalized contact resistance (RCW) for Au (12 kΩ cm) is high in comparison to Ca (7.2 kΩ cm) or Ca/Au (7.5 kΩ cm) electrodes at low gate voltage (VGS=10 V). However, in the strong accumulation regime at high gate voltage (VGS=30 V), its value is nearly independent of the choice of metal electrodes and in a range of 2.2–2.6 kΩ cm. These devices show stable electrical behavior under multiple scans and low threshold voltage instability under electrical bias stress (VDS=VGS=30 V, 1 h) in N2 atmosphere.
Citations
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Journal ArticleDOI
TL;DR: In this article, a study of three soluble fullerenes with varying electron affinity was conducted to assess the impact of electronic structure on device performance and air stability, and it was shown that the air stability of the present series of fullerene derivatives not only depends on the absolute electron affinity of the semiconductor but also on the disorder within the thin-film.
Abstract: The family of soluble fullerene derivatives comprises a widely studied group of electron transporting molecules for use in organic electronic and optoelectronic devices. For electronic applications, electron transporting (n-channel) materials are required for implementation into organic complementary logic circuit architectures. To date, few soluble candidate materials have been studied that fulfill the stringent requirements of high carrier mobility and air stability. Here we present a study of three soluble fullerenes with varying electron affinity to assess the impact of electronic structure on device performance and air stability. Through theoretical and experimental analysis of the electronic structure, characterization of thin-film structure, and characterization of transistor device properties we find that the air stability of the present series of fullerenes not only depends on the absolute electron affinity of the semiconductor but also on the disorder within the thin-film.

20 citations

Journal ArticleDOI
TL;DR: In this article, the critical role of the mixing ratio of the semiconductor and polymer solutions on the performance and electro-mechanical stability of the flexible blend OFETs is investigated.

19 citations

Journal ArticleDOI
TL;DR: In this article, the structural variation between top and bottom contact organic TFTs is examined and analytical models concerning to empirical parameters are discussed for forecasting the performance of organic transistor before a real realization.

17 citations

Journal ArticleDOI
TL;DR: In this paper, a solution-processed n-channel organic thin-film transistors based on a long-chain alkyl-substituted fullerene derivative, C60-fused N-methylpyrrolidine-meta-dodecyl phenyl (C60MC12), by surface modification of an insulator was reported.
Abstract: We report on high-performance solution-processed n-channel organic thin-film transistors based on a long-chain alkyl-substituted fullerene derivative, C60-fused N-methylpyrrolidine-meta-dodecyl phenyl (C60MC12), by surface modification of an insulator. C60MC12 films were fabricated on self-assembled monolayer (SAM)-treated gate insulators by spin-coating, which was facilitated by hydrophilic patterning of the edge of the substrate. X-ray diffraction revealed that the crystallinity of C60MC12 films was improved by SAM treatment. The octadecyltrichlorosilane-treated device demonstrated a high mobility of 0.4–0.5 cm2 V-1 s-1, which is comparable with those of amorphous silicon thin-film transistors. An improvement in bias stress stability by the SAM treatment was also observed.

15 citations

Journal ArticleDOI
14 Jan 2020
TL;DR: In this paper, the authors have discussed the crucial factors in the progression of organic field-effect transistors (OFETs) in flexible portable applications, including operating voltage and processing temperature.
Abstract: Reducing the operating voltage and processing temperature are the crucial factors in the progression of organic field-effect transistors (OFETs) in flexible portable applications. Here, we have dem...

15 citations

References
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Journal ArticleDOI
05 Feb 2009-Nature
TL;DR: A highly soluble and printable n-channel polymer exhibiting unprecedented OTFT characteristics under ambient conditions in combination with Au contacts and various polymeric dielectrics is reported and all-printed polymeric complementary inverters have been demonstrated.
Abstract: Printed electronics is a revolutionary technology aimed at unconventional electronic device manufacture on plastic foils, and will probably rely on polymeric semiconductors for organic thin-film transistor (OTFT) fabrication. In addition to having excellent charge-transport characteristics in ambient conditions, such materials must meet other key requirements, such as chemical stability, large solubility in common solvents, and inexpensive solution and/or low-temperature processing. Furthermore, compatibility of both p-channel (hole-transporting) and n-channel (electron-transporting) semiconductors with a single combination of gate dielectric and contact materials is highly desirable to enable powerful complementary circuit technologies, where p- and n-channel OTFTs operate in concert. Polymeric complementary circuits operating in ambient conditions are currently difficult to realize: although excellent p-channel polymers are widely available, the achievement of high-performance n-channel polymers is more challenging. Here we report a highly soluble ( approximately 60 g l(-1)) and printable n-channel polymer exhibiting unprecedented OTFT characteristics (electron mobilities up to approximately 0.45-0.85 cm(2) V(-1) s(-1)) under ambient conditions in combination with Au contacts and various polymeric dielectrics. Several top-gate OTFTs on plastic substrates were fabricated with the semiconductor-dielectric layers deposited by spin-coating as well as by gravure, flexographic and inkjet printing, demonstrating great processing versatility. Finally, all-printed polymeric complementary inverters (with gain 25-65) have been demonstrated.

2,769 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of organic field effect transistors (OFETs) is examined in terms of field effect mobility and on-off current ratio, and the most prominent fabrication techniques are described.
Abstract: Organic field-effect transistors (OFETs) were first described in 1987. Their characteristics have undergone spectacular improvements during the last two or three years. At the same time, several models have been developed to rationalize their operating mode. In this review, we examine the performance of OFETs as revealed by recently published data, mainly in terms of field-effect mobility and on–off current ratio. We compare the various compounds that have been used as the active component, and describe the most prominent fabrication techniques. Finally, we analyze the charge transport mechanisms in organic solids, and the resulting models of OFETs.

2,380 citations

Journal ArticleDOI
10 Mar 2005-Nature
TL;DR: It is demonstrated that the use of an appropriate hydroxyl-free gate dielectric—such as a divinyltetramethylsiloxane-bis(benzocyclobutene) derivative (BCB; ref. 6)—can yield n-channel FET conduction in most conjugated polymers, revealing that electrons are considerably more mobile in these materials than previously thought.
Abstract: Organic semiconductors have been the subject of active research for over a decade now, with applications emerging in light-emitting displays and printable electronic circuits. One characteristic feature of these materials is the strong trapping of electrons but not holes1: organic field-effect transistors (FETs) typically show p-type, but not n-type, conduction even with the appropriate low-work-function electrodes, except for a few special high-electron-affinity2,3,4 or low-bandgap5 organic semiconductors. Here we demonstrate that the use of an appropriate hydroxyl-free gate dielectric—such as a divinyltetramethylsiloxane-bis(benzocyclobutene) derivative (BCB; ref. 6)—can yield n-channel FET conduction in most conjugated polymers. The FET electron mobilities thus obtained reveal that electrons are considerably more mobile in these materials than previously thought. Electron mobilities of the order of 10-3 to 10-2 cm2 V-1 s-1 have been measured in a number of polyfluorene copolymers and in a dialkyl-substituted poly(p-phenylenevinylene), all in the unaligned state. We further show that the reason why n-type behaviour has previously been so elusive is the trapping of electrons at the semiconductor–dielectric interface by hydroxyl groups, present in the form of silanols in the case of the commonly used SiO2 dielectric. These findings should therefore open up new opportunities for organic complementary metal-oxide semiconductor (CMOS) circuits, in which both p-type and n-type behaviours are harnessed.

2,191 citations

Journal ArticleDOI
TL;DR: New semiconducting liquid-crystalline thieno[3,2-b ]thiophene polymers are reported on, the enhancement in charge-carrier mobility achieved through highly organized morphology from processing in the mesophase, and the effects of exposure to both ambient and low-humidity air on the performance of transistor devices.
Abstract: Organic semiconductors that can be fabricated by simple processing techniques and possess excellent electrical performance, are key requirements in the progress of organic electronics. Both high semiconductor charge-carrier mobility, optimized through understanding and control of the semiconductor microstructure, and stability of the semiconductor to ambient electrochemical oxidative processes are required. We report on new semiconducting liquid-crystalline thieno[3,2-b ]thiophene polymers, the enhancement in charge-carrier mobility achieved through highly organized morphology from processing in the mesophase, and the effects of exposure to both ambient and low-humidity air on the performance of transistor devices. Relatively large crystalline domain sizes on the length scale of lithographically accessible channel lengths (∼200 nm) were exhibited in thin films, thus offering the potential for fabrication of single-crystal polymer transistors. Good transistor stability under static storage and operation in a low-humidity air environment was demonstrated, with charge-carrier field-effect mobilities of 0.2–0.6 cm2 V−1 s−1 achieved under nitrogen.

2,011 citations

Journal ArticleDOI
16 Jul 1998-Nature
TL;DR: In this article, an electrophoretic ink based on the microencapsulation of an electrophic dispersion was used to solve the lifetime issues and allow the fabrication of a bistable electronic display solely by means of printing.
Abstract: It has for many years been an ambition of researchers in display media to create a flexible low-cost system that is the electronic analogue of paper. In this context, microparticle-based displays1,2,3,4,5 have long intrigued researchers. Switchable contrast in such displays is achieved by the electromigration of highly scattering or absorbing microparticles (in the size range 0.1–5 μm), quite distinct from the molecular-scale properties that govern the behaviour of the more familiar liquid-crystal displays6. Microparticle-based displays possess intrinsic bistability, exhibit extremely low power d.c. field addressing and have demonstrated high contrast and reflectivity. These features, combined with a near-lambertian viewing characteristic, result in an ‘ink on paper’ look7. But such displays have to date suffered from short lifetimes and difficulty in manufacture. Here we report the synthesis of an electrophoretic ink based on the microencapsulation of an electrophoretic dispersion8. The use of a microencapsulated electrophoretic medium solves the lifetime issues and permits the fabrication of a bistable electronic display solely by means of printing. This system may satisfy the practical requirements of electronic paper.

1,210 citations