Injection-modulated polarity conversion by charge carrier density control via a self-assembled monolayer for all-solution-processed organic field-effect transistors

Roh, Jeongkyun; Lee, Taesoo; Kang, Chan‐mo; Kwak, Jeonghun; Lang, Philippe; Horowitz, Gilles; Kim, Hyeok; Lee, Changhee

doi:10.1038/srep46365

Cited by 28 publications

(44 citation statements)

References 30 publications

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“…On the contrary, SAMs with electron‐withdrawing terminal groups (–F, –Cl, and –NO 2 ) have the internal dipoles pointing toward the electrode surface and increase its work function. Roh et al successfully modulated the channel type (p‐ or n‐type) in poly{[ N , N ′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicar‐boximide)‐2,6‐diyl]‐alt‐5,5′ ‐(2,2′ ‐bithiophene)} (P(NDI2OD‐T2) or Polyera ActivInk N2200) OFETs by selecting either a thiophenol (TP) or a pentafluorobenzene thiol SAM, Figure a–c . Using silver printed electrodes with a nominal work function of 4.91 eV, TP treatment yielded a work function of 4.66 eV, close to the 4.0 eV LUMO of the semiconductor and resulted in n‐type transport, while PFBT shifted the work function to 5.24 eV, close to the 5.6 eV HOMO level, giving p‐type transport .…”

Section: Reducing Contact Resistance: Electrode Design and Beyondmentioning

confidence: 99%

“…PFBT is a popular SAM incorporated in p‐type OFETs. It is also a fluorine‐substituted SAM but containing five –F atoms on the benzene structure, and it can increase the work function of gold by up to 0.8 eV . Other heavily fluorinated SAMs include 4‐(tri‐ fluoromethyl)‐benzenethiol (TFBT) and 2,3,5,6‐tetrafluoro‐4‐(trifluoromethyl)‐ benzenethiol (TTFP), which were shown to increase the work function, lower contact resistance, and improve OFET performance, as seen in Figure d .…”

Section: Reducing Contact Resistance: Electrode Design and Beyondmentioning

confidence: 99%

“…Pentafluorobenzene thiol (PFBT), with a downward‐facing dipole, shifted the work function close to the semiconductor HOMO and promoted p‐type operation, as seen in c). Adapted with permission . Copyright 2017, Springer Nature.…”

Section: Reducing Contact Resistance: Electrode Design and Beyondmentioning

confidence: 99%

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

Waldrip

Jurchescu

Gundlach

et al. 2019

Adv Funct Materials

238

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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Section: Reducing Contact Resistance: Electrode Design and Beyondmentioning

confidence: 99%

Section: Reducing Contact Resistance: Electrode Design and Beyondmentioning

confidence: 99%

See 1 more Smart Citation

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

Waldrip

Jurchescu

Gundlach

et al. 2019

Adv Funct Materials

238

261

View full text Add to dashboard Cite

show abstract

“…In contrast, the surface potentials of the TP and DT cases were lower than the surface potentials of the PFBT and pristine cases, which could have been due to the relatively electron‐donating character of the benzene‐ring and alkyl‐chain structures in the reactive thiol species, respectively. [ 49,50 ] Such marked differences in kinetic energy were expected to yield a strong difference in terms of charge accumulation or injection of their OFET device performances. The µ FET and V th were influenced by the intrinsic electric field produced by the interfacial properties between S/D electrodes and the active layer.…”

Section: Resultsmentioning

confidence: 99%

Tuning Interfacial Properties by Spontaneously Generated Organic Interlayers in Top‐Contact‐Structured Organic Transistors

Choi

Seo

et al. 2020

Adv Funct Materials

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Controlling the interfacial properties between the electrode and active layer in organic field‐effect transistors (OFETs) can significantly affect their contact properties, resulting in improvements in device performance. However, it is difficult to apply to top‐contact‐structured OFETs (one of the most useful device structures) because of serious damage to the organic active layer by exposing solvent. Here, a spontaneously controlled approach is explored for optimizing the interface between the top‐contacted source/drain electrode and the polymer active layer to improve the contact resistance (RC). To achieve this goal, a small amount of interface‐functionalizing species is blended with the p‐type polymer semiconductor and functionalized at the interface region at once through a thermal process. The RC values dramatically decrease after introduction of the interfacial functionalization to 15.9 kΩ cm, compared to the 113.4 kΩ cm for the pristine case. In addition, the average field‐effect mobilities of the OFET devices increase more than three times, to a maximum value of 0.25 cm2 V−1 s−1 compared to the pristine case (0.041 cm2 V−1 s−1), and the threshold voltages also converge to zero. This study overcomes all the shortcomings observed in the existing results related to controlling the interface of top‐contact OFETs by solving the discomfort of the interface optimization process.

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“…We note, however, that similar values have been previously reported for n-type naphthalene diimide (NDI)-based polymer transistors. [32][33][34][35]…”

Section: Figurementioning

confidence: 99%

Poly(2-alkyl-2-oxazoline) electrode interlayers for improved n-type organic field effect transistor performance

Nam

Rosa

Cho

et al. 2019

Applied Physics Letters

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Thin film interlayer materials inserted at the metal/semiconductor interface provide an effective means to improve charge injection and reduce threshold voltage for organic field-effect transistors. Here we report the use of poly(2-alkyl-2-oxazoline) interlayers for gold electrodes within n-type poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]alt-5,5′-(2,2′-bithiophene)] field-effect transistors. We specifically show that the use of poly(2-ethyl-2-oxazoline) yields a reduction in work function from 5.07 to 4.73 eV (E = 0.34 eV), an increase in electron mobility from 0.04 to 0.15 cm 2 /Vs (3.75 times) and a reduction in threshold voltage from 27.5 to 16.5 V (V = 11V) relative to bare gold. The alkyl side chain of the poly(2-alkyl-2-oxazoline)s has a significant influence on film microstructure and, as a consequence, also device performance. THE MANUSCRIPT Organic field effect transistors (OFETs) are of interest for applications including rollable and foldable information displays and sensors for use in the internet of things (IoT). 1-5 Significant progress in the performance of OFETs has been achieved through fundamental understanding of the device physics and charge transport for organic semiconductors as well as through the rational design and synthesis of new materials. 6-9 Many of the applications envisioned for OFETs are portable electronic devices for which low power consumption is a critical requirement. 10,11 Complementary logic, combining p-type and n-type OFETs, can help to minimize power consumption. However, the performance of n-type OFETs typically lags behind in terms of charge carrier mobility and air stability. 12 High-performance n-type OFETs are, therefore, a key need for the ongoing development of plastic electronics and provide the focus for this paper.

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Injection-modulated polarity conversion by charge carrier density control via a self-assembled monolayer for all-solution-processed organic field-effect transistors

Cited by 28 publications

References 30 publications

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

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

Tuning Interfacial Properties by Spontaneously Generated Organic Interlayers in Top‐Contact‐Structured Organic Transistors

Poly(2-alkyl-2-oxazoline) electrode interlayers for improved n-type organic field effect transistor performance

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