Threshold-Voltage Shifts in Organic Transistors Due to Self-Assembled Monolayers at the Dielectric: Evidence for Electronic Coupling and Dipolar Effects

Aghamohammadi, Mahdieh; Rödel, Reinhold; Zschieschang, Ute; Ocal, Carmen; Boschker, Hans; Weitz, R. Thomas; Barrena, Esther; Klauk, Hagen

doi:10.1021/acsami.5b02747

Cited by 98 publications

(101 citation statements)

References 68 publications

(137 reference statements)

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“…DNTT TFTs prepared with cPVA modified with various agents were fabricated and tested (Figure S22 and Table S6, Supporting Information). The TFTs with fluorine‐terminated (F‐terminated) SAMs had slightly lower μ FET values and tended to have a slightly shift in V th s to positive gate voltages . TFTs with F‐terminated SAMs in general have better bias stabilities than the hydrocarbon SAM‐treated devices .…”

Section: Resultsmentioning

confidence: 99%

Heat‐Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low‐Power Organic Soft Electronics

Kim

Kang

Cho

2019

Adv Funct Materials

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The use in low-power soft electronics of the appropriate insulating polymer materials with a high dielectric constant (k) is considered a practical alternative to that of inorganic dielectric materials, which are brittle and have high processing temperatures. However, the polar surfaces of typical high-k polymer insulators are problematic. Further, it is a huge challenge to control their surface properties without damage because of their soft and chemically fragile nature. Here, a heat-assisted photoacidic oxidation method that can be used to effectively oxidize the outermost surfaces of high-k rubbery polymer films without degradation is presented. The oxidized surfaces prepared with the developed method contain large numbers of hydroxyl groups that enable the subsequent growth of dense and ordered self-assembled monolayers (SAMs) consisting of organosilanes. The whole process modifies the surface characteristics of polymer dielectrics effectively. The mechanisms of the oxidation of polymer surfaces and the subsequent SAM growth process are investigated. The resulting surface-tailored rubbery dielectrics exhibit superior electrical characteristics when used in organic transistors. These results demonstrate that this method can be used to realize practical soft organic electronics based on high-k polymer dielectrics.

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Section: Resultsmentioning

confidence: 99%

Heat‐Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low‐Power Organic Soft Electronics

Kim

Kang

Cho

2019

Adv Funct Materials

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“…In other words, the BGBC structure takes greater advantage of a strong field at the semiconductor/dielectric interface. To increase the strength of the field generated by V GS , high‐ k dielectrics and/or a thin dielectric layer can be used, for example a thin layer of aluminum oxide passivated by an alkylphonsphonic acid SAM for a dielectric thickness down to 5.3 nm . BGBC OFETs of 2,9‐diphenyl‐dinaphtho[2,3‐b:2',3'‐f] thieno[3,2‐b]thiophene (DPh‐DNTT) with SAM gate dielectric, and PFBT‐treated gold source and drain contacts produced lower R C (29 Ω cm) compared to the BGTC counterpart (56 Ω cm).…”

Section: Charge Injection Through a Metal–semiconductor Interfacementioning

confidence: 99%

Contact Resistance in Organic Field‐Effect Transistors: Conquering the Barrier

Waldrip

Jurchescu

Gundlach

et al. 2019

Adv Funct Materials

226

261

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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.semiconductors with superior intrinsic charge transport properties, there is a stringent need to improve the device properties in order to allow organic devices to fulfill their technological prospectives. In the organic semiconductor community, contact resistance (R C ) has come under increased scrutiny as it is apparent that the final device performance is often domi nated by carrier injection, rather than the transport through the semiconductor layer. Contact resistance can impact OFET development in multiple ways. First, if not accounted for, a high contact resistance may lead to inaccurate extraction of the device parameters. Second, any inaccuracies in parameter extraction can have significant consequences on material development, from generating incorrect structure-property relationships to discarding organic semiconductors whose efficient intrinsic electrical properties have been masked by inefficient contacts. Beyond OFET and semiconductor characterization, analog, low power, and high frequency applications require a greater level of device parameter control than has been obtained in typical DC, high-voltage OFETs. For analog applications, e.g., integration of conditioning circuits such as local sense amps for distributed flexible sensor arrays, nonlinearity of the transistor response inhibits proper functioning and limits applicability of common models used to design circuitry. Low power device development for novel materials are hindered by the high voltage turn-on and current suppression in devices with large R C . Considering high-frequency applications, Klauk suggest...

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“…99 The origin of unipolarization was assumed to be characteristic surface potentials induced by the SAMs, which created positive or negative charge depending on the SAMs in the semiconducting layer and acted as a trap site for electron or hole in the ambipolar P3 semiconductor. 100 Utilizing the unipolarization effects of the SAMs, complementary inverters on a substrate with two distinct regions modified with FDTS and MAPS for pull-up and pull-down transistors, respectively, (Figure 12a) were fabricated. Demonstrated by the voltage transfer characteristic (VTC) curve (Figure 12b), an almost ideal inversion with a large voltage gain was observed.…”

Section: ¹2mentioning

confidence: 99%

Thiophene-Fused Naphthalene Diimides: New Building Blocks for Electron Deficient π-Functional Materials

Takimiya

Nakano

2017

Bulletin of the Chemical Society of Japan

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Development of novel π-conjugated building blocks that can be integrated into molecular or macromolecular systems is key to the evolution of new superior organic semiconductors utilized as the active materials in organic electronics devices such as organic field-effect transistors (OFETs), organic photovoltaics (OPVs), and organic thermoelectric (TE) devices. This review affords a brief overview of thiophene-fused naphthalene diimide (NDI), namely naphtho[2,3-b:6,7-b¤]dithiophene diimide (NDTI) and naphtho [2,3-b]thiophene diimide (NTI), recently developed as novel electron deficient building blocks for n-type and ambipolar organic semiconductors. These thiophene-fused NDI building blocks had not been known until 2013 owing to their synthetic difficulty; more precisely, the difficulty in attaching fused-thiophene ring(s) on the NDI core. We have successfully established a thiophene-annulation reaction on ethyne-substituted NDI derivatives, which allows us to elaborate various NDTI and NTI derivatives. The key features of these building blocks are low-lying energy levels of lowest unoccupied molecular orbitals (LUMO, 3.84.1 eV below the vacuum level) and easy functionalizability of the thiophene ¡-positions, which allows their derivatives and polymers to conjugate efficiently with additional π-and comonomer units. These features make the NDTI-and NTIderivatives and polymers promising n-type and ambipolar materials for OFETs and acceptors for OPVs. In fact, various useful materials have already been derived from the NDTI and NTI building blocks: air-stable n-type small molecules and polymers with high electron mobility (³0.8 cm 2 V ¹1 s ¹1), ambipolar oligomers and polymers with well-balanced hole and electron mobilities, doped n-type semiconductors affording bulk conductors applicable to n-type TE materials, and electron acceptor molecules and polymers for OPVs showing promising power conversion efficiencies of up to 9%. These impressive and diversified device performances testify the usefulness of thiophene-fused NDI building blocks in the development of new electron deficient π-functional materials.

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Threshold-Voltage Shifts in Organic Transistors Due to Self-Assembled Monolayers at the Dielectric: Evidence for Electronic Coupling and Dipolar Effects

Cited by 98 publications

References 68 publications

Heat‐Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low‐Power Organic Soft Electronics

Heat‐Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low‐Power Organic Soft Electronics

Contact Resistance in Organic Field‐Effect Transistors: Conquering the Barrier

Thiophene-Fused Naphthalene Diimides: New Building Blocks for Electron Deficient π-Functional Materials

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