Direct Structural Mapping of Organic Field‐Effect Transistors Reveals Bottlenecks to Carrier Transport

Li, Ruipeng; Ward, Jeremy W.; Smilgies, Detlef‐M.; Payne, Marcia M.; Anthony, John E.; Jurchescu, Oana D.; Amassian, Aram

doi:10.1002/adma.201201856

Cited by 75 publications

(110 citation statements)

References 28 publications

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“…Recently, Headrick and colleagues 30 reported stresses and buckling occurred in thin films of TIPS-pentacene during hollow capillary writing. The time resolution in the study was approximately 0.3 s. However, successful investigation of the crystallization process in the presence of the laterally moving crystal growth front requires the use of high-speed microbeam X-ray-scattering techniques with millisecond time resolution 39 .…”

Section: Resultsmentioning

confidence: 99%

“…In situ time-resolved measurements of thin-film growth during solution shearing were performed at beamline D1 at the Cornell High Energy Synchrotron Source (CHESS) using mGIWAXS 28,39 . An X-ray microbeam focused to a 15 Â 15 mm 2 spot is required, as the evaporation front (meniscus) can be as small as 100 mm wide (Supplementary Movie 1).…”

Section: Resultsmentioning

confidence: 99%

“…An X-ray microbeam focused to a 15 Â 15 mm 2 spot is required, as the evaporation front (meniscus) can be as small as 100 mm wide (Supplementary Movie 1). The microbeam was focused by using a single-bounce X-ray capillary 39 . The sample was mounted on the temperature-controlled solutionshearing setup, and thin-film formation was viewed with an optical microscope during solution shearing 28 .…”

Section: Resultsmentioning

confidence: 99%

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One-dimensional self-confinement promotes polymorph selection in large-area organic semiconductor thin films

RuiPeng²,

et al. 2014

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A crystal's structure has significant impact on its resulting biological, physical, optical and electronic properties. In organic electronics, 6,13(bis-triisopropylsilylethynyl)pentacene (TIPS-pentacene), a small-molecule organic semiconductor, adopts metastable polymorphs possessing significantly faster charge transport than the equilibrium crystal when deposited using the solution-shearing method. Here, we use a combination of high-speed polarized optical microscopy, in situ microbeam grazing incidence wide-angle X-ray-scattering and molecular simulations to understand the mechanism behind formation of metastable TIPS-pentacene polymorphs. We observe that thin-film crystallization occurs first at the air-solution interface, and nanoscale vertical spatial confinement of the solution results in formation of metastable polymorphs, a one-dimensional and large-area analogy to crystallization of polymorphs in nanoporous matrices. We demonstrate that metastable polymorphism can be tuned with unprecedented control and produced over large areas by either varying physical confinement conditions or by tuning energetic conditions during crystallization through use of solvent molecules of various sizes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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One-dimensional self-confinement promotes polymorph selection in large-area organic semiconductor thin films

RuiPeng²,

et al. 2014

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“…In-plane structural inhomogeneity induced by the dielectric surface has also been reported. 21 The electric field in OFET is central for charge generation and charge mobility according to Frenkel-Poole theory. 22 The longitudinal electrostatic potential drops rapidly at grain boundaries thus generating a step-wise electric field profile across the OFET channel 23 with practically no-field within the domains and large field across boundaries.…”

Section: Introductionmentioning

confidence: 99%

Changes of the Molecular Structure in Organic Thin Film Transistors during Operation

et al. 2015

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Thin films of organic semiconductors have been widely studied at different length scales for improving the electrical response of devices based on them. Hitherto, a lot of knowledge has been gained about how molecular packing, morphology, grain boundaries, and defects affect the charge transport in organic thin film transistors. However, little is known about the impact of an electric field on the organic semiconductor microstructure and the consequent effect on the device performances. To fill this gap, we investigated the evolution of the structure of pentacene thin film transistors during device operation by in situ real time X-ray diffraction measurements and theoretical calculations. We observed for the first time the occurrence of a reversible structural strain taking place during the bias application mainly due to reorientation at the terrace edges of monolayer islands under the effect of electrical field. Strain exhibits the same trend of the threshold voltage hinting to the existence of a direct correlation between the phenomenon of bias stress and the structural modification.2

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“…[33][34][35] Li et al treated the electrodes with fluorine substituted benzene thiol and effectively improved the texture from the contacts extending to thwe channel, as well as the performance of corresponding solution casted BC transistors. [30,36,37] Here, we report a simple method to improve the continuity of organic films at the lateral interfaces of electrode/organic through incorporating an organic inducing layer. Inserting an inducing layer has been widely applied in top contact transistors and received considerable attentions.…”

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confidence: 99%

High‐Performance Bottom‐Contact Organic Thin‐Film Transistors by Improving the Lateral Contact

Zhang

Wang

Zhou

et al. 2017

Adv Elect Materials

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prepatterned electrodes on the substrates generate artificial steps that significantly affect the morphological uniformity and continuity of the organic active layer at the electrode/organic interfaces, causing large contact resistance. The most common solution is to modify the electrodes, e.g., chemical bonding of thiols on gold, inserting buffer layer on the electrodes, or applying conductive materials such as graphene, polypyrrole as electrodes. [2,10, These approaches could either realize a good energy level alignment or improve the interface morphology to decrease the contact resistance. Nevertheless, the performances of the BC transistors are still insufficient to match the application requirements.It is known that the resistance of the transistors consists of channel resistance and contact resistance. The latter is determined by the carrier injection from the interfaces of the organic/electrode: the top injection and the side injection. [22] With regard to the side injection, a major issue is the morphology discontinuity near the edge of the electrodes. Previously, Kudo and co-workers proposed a method that embedding electrodes into the dielectric layer to achieve a planar interface and obtained a mobility ≈0.48 cm 2 V −1 s −1 (in saturate regime) for pentacene, but this will induce relatively complicate patterning process. [33][34][35] Li et al. treated the electrodes with fluorine substituted benzene thiol and effectively improved the texture from the contacts extending to thwe channel, as well as the performance of corresponding solution casted BC transistors. [30,36,37] Here, we report a simple method to improve the continuity of organic films at the lateral interfaces of electrode/organic through incorporating an organic inducing layer. Inserting an inducing layer has been widely applied in top contact transistors and received considerable attentions. [38][39][40] Herein, the organic layer which forms lamellar grains from the edge of the photolithographypatterned electrodes was deposited prior to depositing the active layer. The following organic semiconductor layer grown on the inducing layer formed lamellar films on the inducing layer, enabling a good contact between the electrodes and the organic semiconductor thin films. As a result, a remarkable decrement of the contact resistance is achieved. Together with the improved film ordering by weak epitaxy on the inducing layer in the channel area, we achieved high performance bottom contact thin film transistors with the maximum mobility exceeding 1 cm 2 V −1 s −1 for pentacene in ambient condition, which is comparable to the top contact ones.One of the main challenges to achieve high-performance bottom-contact transistors involves the organic/electrodes contacts. This study provides a simple approach to address the contact issue by incorporating an inducing layer prior to the organic semiconductor deposition. The molecules of the inducing layer nucleate into lamellar grains from the edge to the channel, resulting in a good morphological contact to th...

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Direct Structural Mapping of Organic Field‐Effect Transistors Reveals Bottlenecks to Carrier Transport

Cited by 75 publications

References 28 publications

One-dimensional self-confinement promotes polymorph selection in large-area organic semiconductor thin films

One-dimensional self-confinement promotes polymorph selection in large-area organic semiconductor thin films

Changes of the Molecular Structure in Organic Thin Film Transistors during Operation

High‐Performance Bottom‐Contact Organic Thin‐Film Transistors by Improving the Lateral Contact

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