Self-assembled monolayers as interfaces for organic opto-electronic devices

Zuppiroli, L.; Si‐Ahmed, Lynda; Kamarás, Katalin; Nüesch, Frank; Bussac, M. N.; Adès, D.; Siove, Alain; Moons, Ellen; Grätzel, Michaël

doi:10.1007/s100510050962

Cited by 146 publications

(112 citation statements)

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“…8a, a surface dipole layer on the metal can alter the effective work function of the metal, and therefore naively the band alignment at the interface. This idea was first demonstrated in OLED devices over 10 years ago, 20 and has received much attention from that community, [21][22][23][24] with comparably little work done in FET structures.…”

Section: Controlling Interfacial Energeticsmentioning

confidence: 99%

Contact effects in polymer field-effect transistors

et al. 2006

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Contact resistances often contribute significantly to the overall device resistance in organic field-effect transistors (OFETs). Understanding charge injection at the metal-organic interface is critical to optimizing OFET device performance. We have performed a series of experiments using bottom-contact poly(3-hexylthiophene) (P3HT) OFETs in the shallow channel limit to examine the injection process. When contacts are ohmic we find that contact resistivity is inversely proportional to carrier mobility, consistent with diffusion-limited injection. However, data from devices with other electrode materials indicate that this simple picture is inadequate to describe contacts with significant barriers. A generalized transmission line method allows the analysis of nonohmic contacts, and we find reasonable agreement with a model for injection that accounts for the hopping nature of conduction in the polymer. Variation of the (unintentional) dopant concentration in the P3HT can significantly alter the injection process via changes in metal-organic band alignment. At very low doping levels, transport suggests the formation of a barrier at the Au/P3HT interface, while Pt/P3HT contacts remain ohmic with comparatively low resistance. We recently observed that self-assembled monolayers on the metal source/drain electrodes can significantly decrease contact resistance and maintain ohmic conduction under conditions that would result in nonohmic, high resistance contacts to untreated electrodes. Finally, we discuss measurements on extremely short channel devices, in the initial steps toward examining transport through individual polymer chains.

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Section: Controlling Interfacial Energeticsmentioning

confidence: 99%

Contact effects in polymer field-effect transistors

et al. 2006

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“…Indeed, many efforts to improve OLEDs have been directed toward the optimization of the inorganic-organic interfaces. For example, different treatments of the indium tin oxide ͑ITO͒ anode, such as oxygen plasma cleaning, 3 or grafting of monomolecular layers as interfaces 4 have been tried.…”

Section: Introductionmentioning

confidence: 99%

Competition between excitons and exciplexes: Experiments on multilayered organic light emitting diodes

Castellani

Berner²

2007

Journal of Applied Physics

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The electronic processes responsible for charge transport and electroluminescence in multilayered organic light emitting diodes ͑OLEDs͒ are very sensitive to the properties of the organic heterojunction. In particular, the height of the energy barrier affects the way in which electrons and holes meet at the heterojunction, the way in which the barrier is crossed, and the probability for photon creation. We investigate these aspects experimentally using a family of OLED devices in which different hole transporting materials are used in otherwise identical device architectures to vary the interfacial hole barrier over a wide energy range. We find that the quantum efficiency of the device is maximum for low-energy barriers and drops for high barrier values where a redshifted electroluminescence spectrum is observed. This shift is attributed to exciplex generation at the heterojunction. The contributions of exciton and exciplex annihilation in radiative and nonradiative channels to the charge flow within the heterojunction region are separated and quantified.

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“…SAM modification of a metal surface offers a better possibility to improve the performance of OE devices as well [518,[562][563][564][565][566][567][568][569][570][571][572][573][574]. The formation of SAMs on a metal surface, in the present context of OFETs, is basically meant for improving the contact properties across a semiconductor-metal interface.…”

Section: Interface Engineering For Os Devicesmentioning

confidence: 99%

“…In order to adjust the electrical conditions at different interfaces encountered in practice, various types of SAMs were developed in the past and used in different contexts such as patterning of nanoscale devices, corrosion prevention, and controlling surface properties [518,[552][553][554][562][563][564][565][566][567][568][569][570][571][572][573][574]. SAM modification of a metal surface offers a better possibility to improve the performance of OE devices as well [518,[562][563][564][565][566][567][568][569][570][571][572][573][574].…”

Section: Interface Engineering For Os Devicesmentioning

confidence: 99%

“…Consequent upon using the above criteria of interface engineering in OS device fabrications, the influence of SAMs on oxides such as SiO 2 , Al 2 O 3 , and TiO 2 [563,[565][566][567][568][569], metals such as Au and Pt [562,570,572,573,579], and native oxides of metals such as Cu, Ag, Ti, Al, and Fe were investigated in detail [562,571]. For instance, in the case of Mo thin films, although it has a low resistivity of 5 μΩ cm, its work function is in the range of 4.6 to 4.9 eV [581], resulting in a larger barrier height to hole injection in pentacene than that with Au.…”

Section: Interface Engineering For Os Devicesmentioning

confidence: 99%

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Organic semiconductors for device applications: current trends and future prospects

Ahmad

2014

Journal of Polymer Engineering

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Abstract:With the rich experience of developing silicon devices over a period of the last six decades, it is easy to assess the suitability of a new material for device applications by examining charge carrier injection, transport, and extraction across a practically realizable architecture; surface passivation; and packaging and reliability issues besides the feasibility of preparing mechanically robust wafer/substrate of single-crystal or polycrystalline/ amorphous thin films. For material preparation, parameters such as purification of constituent materials, crystal growth, and thin-film deposition with minimum defects/ disorders are equally important. Further, it is relevant to know whether conventional semiconductor processes, already known, would be useable directly or would require completely new technologies. Having found a likely candidate after such a screening, it would be necessary to identify a specific area of application against an existing list of materials available with special reference to cost reduction considerations in large-scale production. Various families of organic semiconductors are reviewed here, especially with the objective of using them in niche areas of large-area electronic displays, flexible organic electronics, and organic photovoltaic solar cells. While doing so, it appears feasible to improve mobility and stability by adjusting π-conjugation and modifying the energy bandgap. Higher conductivity nanocomposites, formed by blending with chemically conjugated C-allotropes and metal nanoparticles, open exciting methods of designing flexible contact/interconnects for organic and flexible electronics as can be seen from the discussion included here.

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Self-assembled monolayers as interfaces for organic opto-electronic devices

Abstract: PACS. 73.30.+y Surface double layers, Schottky barriers, and work functions, 73.61.Ph Polymers; organic compounds,

Cited by 146 publications

References 0 publications

Contact effects in polymer field-effect transistors

Contact effects in polymer field-effect transistors

Competition between excitons and exciplexes: Experiments on multilayered organic light emitting diodes

Organic semiconductors for device applications: current trends and future prospects

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