Interface Engineering of Semiconductor/Dielectric Heterojunctions toward Functional Organic Thin-Film Transistors

Zhang, Hongtao; Guo, Xuefeng; Hui, Jingshu; Hu, Shuxin; Xu, Wei; Zhu, Daoben

doi:10.1021/nl2028798

Cited by 142 publications

(117 citation statements)

References 57 publications

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“…12 Apart from this it is well-known that, in a typical OFET, the first few layers of molecules at the dielectricsemiconductor interface are also responsible for charge transport. 13 Herein, we report the synthesis of NMeCy2 and fabrication of n-channel OFETs using a stack of trilayer gate dielectric system (Al 2 O 3 /PVA/PMMA) to achieve high mobility and low operating voltage. Among high-k dielectrics, inorganic metal oxides are generally preferred.…”

Section: ■ Introductionmentioning

confidence: 99%

Large-Scale Molecular Packing and Morphology-Dependent High Performance Organic Field-Effect Transistor by Symmetrical Naphthalene Diimide Appended with Methyl Cyclohexane

2015

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The influence of structural ordering of methyl cyclohexane appended naphthalene diimide (NMeCy2) thin films and their correlation with enhanced device performances are presented here. The vacuum-deposited thin-film microstructure and morphology of NMeCy2 have been investigated using thin-film X-ray diffraction (XRD), atomic force microscopy (AFM), and field emission scanning electron microscopy (FESEM) and were comparable with the bulk-phase crystalline structure and packing of NMeCy2. The organic field-effect transistor (OFET) fabricated on a glass substrate consists of a bilayer polymer dielectric poly(methyl methacrylate) (PMMA) over poly(vinyl alcohol) (PVA) and an inorganic high-k dielectric Al 2 O 3 as the third layer. NMeCy2 thermally deposited at an optimized substrate temperature (T sub ) of 60°C displayed excellent molecular packing over a large area that resulted in the improved field-effect performance with electron mobility (μ e ) value of 0.6 cm 2 V −1 s −1 and current on/off ratio (I on/off ) of 10 6 via modifications in dielectric configuration. Furthermore, the device afforded an unprecedented threshold voltage (V Th ) of 5.23 V with this material. We have been successful in developing a facile, reliable, and cheap method to tune the dielectric features which can culminate in improved field-effect transport properties. ■ INTRODUCTIONElectronic devices based on small organic molecules and polymers have received considerable attention in recent years due to their low cost and milder operating conditions. Particularly, small molecule based organic semiconductors (OSCs) are versatile, inexpensive, reliable, easily functionalized, and used as active materials in organic light-emitting devices (OLEDs), 1 organic photovoltaics (OPVs), 2 and organic fieldeffect transistors (OFETs). 3 The key problems of these molecules are the low mobility and low environmental stability. High mobility in OFETs is a prerequisite for fast response in high speed device applications. On the other hand, OFETs impose serious limitations to their practical applications due to the high operating voltage and high threshold voltage. Serious efforts have been devoted by researchers to improve these factors. This can be achieved by designing molecules with superior properties, device engineering, controlling the roughness and morphology of the dielectric, and OSC layers. The growth of OSCs and the alignment of crystalline layers on the dielectric surfaces are the key requirements for achieving high mobility. 4 Generally, the hydrophobic surface is more favorable for the growth of OSCs than hydrophilic surfaces. Highly compact well-organized molecular packing among adjacent molecules with significant π-orbital overlap and the absence of grain boundaries facilitate efficient charge transport enabling high mobility. 5 The low operating voltage is one of the main criteria for the integrated digital circuits and biosensor applications. The reduction in the threshold voltage and operating voltage can be achieved by using high-k dielectri...

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Section: ■ Introductionmentioning

confidence: 99%

Large-Scale Molecular Packing and Morphology-Dependent High Performance Organic Field-Effect Transistor by Symmetrical Naphthalene Diimide Appended with Methyl Cyclohexane

2015

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“…[23][24][25][26][27] The latter approach seems to be the most promising. It is known that the highest density of charge carriers in operating OFET fl ows in a few molecular layers of semiconductor adjacent to dielectric.…”

mentioning

confidence: 99%

OFET‐Based Memory Devices Operating via Optically and Electrically Modulated Charge Separation between the Semiconductor and 1,2‐bis(Hetaryl)ethene Dielectric Layers

Frolova

Rezvanova

Ширинян

et al. 2015

Adv Elect Materials

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semiconductor and dielectric. [23][24][25][26][27] The latter approach seems to be the most promising. It is known that the highest density of charge carriers in operating OFET fl ows in a few molecular layers of semiconductor adjacent to dielectric. [ 28 ] Therefore, photoisomerization of a photochromic compound at the dielectric/semiconductor interface changes signifi cantly electrical characteristics of the conducting channel (density of traps/carriers, electrical permittivity, capacitance) and the device itself thus providing the required photoswitching effect.While comparing the characteristics of the OFET-based memory elements, few important parameters should be considered. First of all, it is a switching coeffi cient defi ned as k sw = I DS (1)/ I DS (2), where I DS (1) and I DS (2) correspond to the drain currents of the OFET in states 1 and 2, respectively, measured at the same gate voltage V GS = const, which shows how strong is the hysteresis in the electrical characteristics of the transistor or how wide is the memory window. The device operating voltages, a programming speed, and a long-term stability of the distinct electrical states (retention characteristics) are also crucially important.Analyzing previous reports on the OFET-based optical memories comprising photochromic materials, one can notice their low switching coeffi cients which stay typically below 10 and hardly exceed 100 for the best examples (Table S1, Supporting Information). These devices typically operate at high voltages (30-100 V), while their programming is very slow and requires light illumination within tens of seconds or even minutes. To make this type of memory elements more interesting for practical applications one has to improve signifi cantly their characteristics. We have reported very recently memory elements based on a photochromic spirooxazine which showed decent operating voltages (<5 V) and reasonably high switching coefficients of ≈10 3 . [ 29 ] Unfortunately, the programming speeds were still rather low mainly due to fundamental limitations of the used materials and the device architecture.Here we present a concept of the memory elements operating via optically and electrically triggered charge separation between the organic semiconductor ([60]fullerene) and the photochromic dielectric (specially designed 1,2-bis(hetaryl) ethene) layers. The proposed approach allowed us to decrease the device programming time by three orders of magnitude down to few milliseconds with a high potential to reach practically interesting microsecond operation regime. Additionally, the designed devices showed exceptionally wide memory windows refl ected by the switching coeffi cients of ≈10 5 at reasonably low operation voltages (3-10 V).

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“…These features can be optimized by achieving control over the packing of SAMs on the NPs (7). When NPs are integrated in a device, they can, for example, act as charge storage sites-i.e., trapping charges centers, allowing the system to act as a memory (9, 10).The incorporation of photochromic molecules into electronic devices to confer them a photoresponsive nature has been recently explored (11)(12)(13)(14). Among photochromic systems (15-18), azobenzene derivatives are known to undergo isomerization from trans to cis form, and vice versa, under illumination at a specific wavelength, as well as from cis to trans with temperature (15).…”

mentioning

confidence: 99%

Optically switchable organic field-effect transistors based on photoresponsive gold nanoparticles blended with poly(3-hexylthiophene)

Raimondo

Crivillers

Reinders

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Interface tailoring represents a route for integrating complex functions in systems and materials. Although it is ubiquitous in biological systems-e.g., in membranes-synthetic attempts have not yet reached the same level of sophistication. Here, we report on the fabrication of an organic field-effect transistor featuring dualgate response. Alongside the electric control through the gate electrode, we incorporated photoresponsive nanostructures in the polymeric semiconductor via blending, thereby providing optical switching ability to the device. In particular, we mixed poly(3-hexylthiophene) with gold nanoparticles (AuNP) coated with a chemisorbed azobenzene-based self-assembled monolayer, acting as traps for the charges in the device. The light-induced isomerization between the trans and cis states of the azobenzene molecules coating the AuNP induces a variation of the tunneling barrier, which controls the efficiency of the charge trapping/detrapping process within the semiconducting film. Our approach offers unique solutions to digital commuting between optical and electric signals.O rganic field-effect transistors (OFETs) are basic building blocks for logic applications and for the development of electronic technologies based on soft matter (1-4). Currently, the greatest challenges in the field are the achievement of higher device performance and the development of devices featuring uncommon and multiple functionalities (5). In this regard, hybrid organic-inorganic materials are gaining much attention because, besides their easy processing, they can take advantage of the tunability of the chemical properties of the components, and thus of the material as a whole. Nanoparticles (NPs) of different materials (gold, silver, metal oxides, etc.) can be coated with selfassembled monolayers (SAMs) of a given molecular system, thereby providing them additional functions such as a specific surface energy or optoelectronic properties (6-8). These features can be optimized by achieving control over the packing of SAMs on the NPs (7). When NPs are integrated in a device, they can, for example, act as charge storage sites-i.e., trapping charges centers, allowing the system to act as a memory (9, 10).The incorporation of photochromic molecules into electronic devices to confer them a photoresponsive nature has been recently explored (11)(12)(13)(14). Among photochromic systems (15-18), azobenzene derivatives are known to undergo isomerization from trans to cis form, and vice versa, under illumination at a specific wavelength, as well as from cis to trans with temperature (15). In the last few years, we have extensively investigated the thiol-substituted azo-biphenyl (AZO, Fig. 1A) when chemisorbed on gold surfaces (19)(20)(21)(22). We demonstrated that such a SAM chemisorbed on the planar source and drain electrodes of an OFET can be used to modulate optically the charge injection at the metal-semiconductor interface because of the different tunneling barrier of the cis and trans SAMs (19). However, the observed light-modul...

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Interface Engineering of Semiconductor/Dielectric Heterojunctions toward Functional Organic Thin-Film Transistors

Cited by 142 publications

References 57 publications

Large-Scale Molecular Packing and Morphology-Dependent High Performance Organic Field-Effect Transistor by Symmetrical Naphthalene Diimide Appended with Methyl Cyclohexane

Large-Scale Molecular Packing and Morphology-Dependent High Performance Organic Field-Effect Transistor by Symmetrical Naphthalene Diimide Appended with Methyl Cyclohexane

OFET‐Based Memory Devices Operating via Optically and Electrically Modulated Charge Separation between the Semiconductor and 1,2‐bis(Hetaryl)ethene Dielectric Layers

Optically switchable organic field-effect transistors based on photoresponsive gold nanoparticles blended with poly(3-hexylthiophene)

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