Bias-Stress Effect in 1,2-Ethanedithiol-Treated PbS Quantum Dot Field-Effect Transistors

Osedach, Timothy P.; Zhao, Ni; Andrew, Trisha L.; Brown, Patrick R.; Wanger, Darcy D.; Strasfeld, David B.; Chang, Liang-Yi; Bawendi, Moungi G.; Bulović, Vladimir

doi:10.1021/nn3008788

Cited by 103 publications

(126 citation statements)

References 42 publications

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“…Moreover, previous measurements of the PbS QD FETs with different gate dielectric materials revealed that the transient current decay is independent of the choice of dielectric. 13 Therefore, our measured transient phenomena are due to the intrinsic properties of PbS QDs.…”

Section: Nano Lettersmentioning

confidence: 95%

“…2,11 In FETs that operate under dark conditions, although it has been recently observed that certain deep defect states can actually assist carrier transport, 7,12 QD films still suffer from significant hysteresis effects where the source-drain current decays substantially in the scale of seconds after charge injection. 13 These effects were found to be independent of the gate dielectric and were thus attributed to the intrinsic properties of PbS QDs. However, no quantitative information on carrier density was presented, and the carrier trapping mechanism is still unresolved.…”

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confidence: 94%

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Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors

et al. 2015

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Noncrystalline semiconductor materials often exhibit hysteresis in charge transport measurements whose mechanism is largely unknown. Here we study the dynamics of charge injection and transport in PbS quantum dot (QD) monolayers in a field effect transistor (FET). Using Kelvin probe force microscopy, we measured the temporal response of the QDs as the channel material in a FET following step function changes of gate bias. The measurements reveal an exponential decay of mobile carrier density with time constants of 3−5 s for holes and ∼10 s for electrons. An Ohmic behavior, with uniform carrier density, was observed along the channel during the injection and transport processes. These slow, uniform carrier trapping processes are reversible, with time constants that depend critically on the gas environment. We propose that the underlying mechanism is some reversible electrochemical process involving dissociation and diffusion of water and/or oxygen related species. These trapping processes are dynamically activated by the injected charges, in contrast with static electronic traps whose presence is independent of the charge state. Understanding and controlling these processes is important for improving the performance of electronic, optoelectronic, and memory devices based on disordered semiconductors.

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Section: Nano Lettersmentioning

confidence: 95%

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confidence: 94%

Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors

et al. 2015

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“…43,44 The transients are also thermally activated (Supporting Information Figures S5 and S6). Activated I D transients in PbX QD FETs have been observed by others and attributed to a barrier to trapping, 42 thermally activated ligand rearrangements, 43 or QD motion. Below ∼150 K, the transients were greatly suppressed for FETs without ALD and often completely eliminated for infilled FETs.…”

mentioning

confidence: 99%

PbSe Quantum Dot Field-Effect Transistors with Air-Stable Electron Mobilities above 7 cm² V^–1 s^–1

Liu¹,

Tolentino²,

Gibbs³

et al. 2013

Nano Lett.

226

322

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PbSe quantum dot (QD) field effect transistors (FETs) with air-stable electron mobilities above 7 cm 2 V −1 s −1 are made by infilling sulfide-capped QD films with amorphous alumina using lowtemperature atomic layer deposition (ALD). This high mobility is achieved by combining strong electronic coupling (from the ultrasmall sulfide ligands) with passivation of surface states by the ALD coating. A series of control experiments rule out alternative explanations. Partial infilling tunes the electrical characteristics of the FETs. KEYWORDS: Quantum dots, nanocrystals, lead selenide, field-effect transistors, solar cells T he recent introduction of metal chalcogenide complexes (MCCs) as ligands for colloidal quantum dots (QDs) 1 has triggered a flurry of research into inorganic ligands for fabricating high-performance all-inorganic QD solids for optoelectronic applications. 2−4 In addition to several demonstrations of MCC efficacy by Talapin and co-workers, 5−8 a variety of metal-free inorganic ions including chalcogenides, 9,10 halides, 11 thiocyanate, 12−14 and trialkyl oxonium 15 have been shown in initial studies to provide generally better performance in CdX and PbX (X = S, Se, Te) QD field-effect transistors (FETs) 6,7,12−14 and solar cells 11 than the small molecules, such as hydrazine 16 and 1,2-ethanedithiol (EDT), 17,18 traditionally used to replace the long-chain insulating organic ligands inherited from QD synthesis. Ionic inorganic ligands offer several key advantages over neutral molecular ligands. First, many inorganic ligands are ultrasmall and enable strong electronic coupling between QDs in films, which favors highmobility transport. Second, inorganic ions can quantitatively replace native long-chain ligands on the QD surface to produce charge-stabilized colloidal QD suspensions in polar media, in principle allowing the direct formation of conductive QD films from solution without the need for postassembly chemical or thermal treatments that can inhibit charge transport by increasing spatial and energetic disorder in the films. In practice, however, thermal treatments (150−300°C) are typically needed to achieve good transport in all-inorganic QD solids. Also, solution-phase exchange has so far failed to yield stable all-inorganic PbX QD colloids except with select hydrazine-free MCCs or mixed chalcogenide ions, 5,13 so postassembly ("solid state") ligand exchange has been employed instead to make PbX QD devices. 10−13,15 A third advantage of inorganic ligands is that they decompose, evaporate, or assimilate into the QDs at relatively low temperatures to create functional inorganic matrices (e.g., with MCCs) or direct QD−QD contact and partial QD necking/fusion (e.g., with S 2− and SCN − ). Despite the large site energy disorder induced by such annealing, 7,14,19 the electronic properties of films made with this approach may be adequate for many applications, including high-efficiency solar energy conversion. Recent reports of record mobilities for electrons in CdSe, 7,14 holes in PbX, 12,1...

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“…Thus, proper balancing of the charge carrier concentrations (mobilities) is necessary. The commonly used thiols mostly result in p-type materials [63,121], while hydrazine [66] and halides [122] were shown to be n-type dopants.…”

Section: The Role Of Surface Chemistrymentioning

confidence: 99%

“…On the other hand, oxygen/water can be adsorbed on the QD surface causing serious electron trapping [124]. Thiol crosslinkers are shown to passivate the surface against oxidation [69], nevertheless the transport in these samples is still limited by the electron trapping, and not by the hole current [121]. When halogenides are introduced to the latter stages of synthesis, they can fill vacancies on the QD surface, showing a similar passivation effect [113,125].…”

Section: The Role Of Surface Chemistrymentioning

confidence: 99%

Colloidal Inorganic–Organic Hybrid Solar Cells

Balazs

Speirs

Loi

2014

Organic and Hybrid Solar Cells

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Bias-Stress Effect in 1,2-Ethanedithiol-Treated PbS Quantum Dot Field-Effect Transistors

Cited by 103 publications

References 42 publications

Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors

Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors

PbSe Quantum Dot Field-Effect Transistors with Air-Stable Electron Mobilities above 7 cm² V^–1 s^–1

Colloidal Inorganic–Organic Hybrid Solar Cells

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Bias-Stress Effect in 1,2-Ethanedithiol-Treated PbS Quantum Dot Field-Effect Transistors

Cited by 103 publications

References 42 publications

Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors

Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors

PbSe Quantum Dot Field-Effect Transistors with Air-Stable Electron Mobilities above 7 cm2 V–1 s–1

Colloidal Inorganic–Organic Hybrid Solar Cells

Contact Info

Product

Resources

About

PbSe Quantum Dot Field-Effect Transistors with Air-Stable Electron Mobilities above 7 cm² V^–1 s^–1