Exceptionally Mild Reactive Stripping of Native Ligands from Nanocrystal Surfaces by Using Meerwein’s Salt

Rosen, Evelyn L.; Buonsanti, Raffaella; Llordés, Anna; Sawvel, April M.; Milliron, Delia J.; Helms, Brett A.

doi:10.1002/anie.201105996

Cited by 261 publications

(329 citation statements)

References 53 publications

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“…16,17 We would like to emphasize that the procedure presented here does not involve annealing in air or other less controlled oxidation techniques applied previously. 6,18 Rather, the carrier concentration is fixed after brief exposure (∼3 s) to the ligand exchange solution. When kept under inert conditions, MeO À -capped PbSe QDS exhibit stability of optical and electrical properties for weeks.…”

Section: Discussionmentioning

confidence: 99%

Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

et al. 2013

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We present a facile procedure to fabricate p-type PbSe-based quantum dot solids with mobilities as large as 0.3 cm2 V–1 s–1. Upon partial ligand exchange of oleate-capped PbSe quantum dots with the methoxide ion, we observe a pronounced red shift in the excitonic transition in conjunction with a large increase in conductivity. We show that there is little correlation between these two phenomena and that the electronic coupling energy in PbSe quantum dot solids is much smaller than often assumed. However, we observe for the first time a nonmonotonic size dependence of the hole mobility, illustrating that coupling can nonetheless be dominant in determining the transport characteristics. We attribute these effects to a decrease in charging energy and interparticle spacing, leading to enhanced electronic coupling on one hand and enhanced dipole interactions on the other hand, which is held responsible for the majority of the red shift.

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Section: Discussionmentioning

confidence: 99%

Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

et al. 2013

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“…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, 12,15 and electrons in PbSe 20 QD films (∼30, 3−4, and 5−10 cm 2 V −1 s −1 , respectively) may also reflect the onset of extended state or even bandlike transport (however, see ref 19), and together illustrate the promise of allinorganic QD solids as a technology platform for highperformance, low-cost, large-area optoelectronics.The use of ultrasmall inorganic ligands is not enough to guarantee high carrier mobility and good transport in QD films, even in the limit of perfect QD monodispersity. This is because surface states within the QD band gap (donors, acceptors, traps, recombination centers) can dominate transport and offset the advantage of strong electronic coupling from compact ligands, direct interdot contact, and QD necking.…”

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confidence: 99%

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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.

227

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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“…Until recently, this has posed a significant challenge to using these colloidal inks as technologically viable electronic materials for devices 12 and integrated circuitry 13 . Advances in ligand chemistry have shown that the original, long ligands used in synthesis can be replaced by shorter inorganic ligands [14][15][16][17] either in solution, and still maintain solution dispersibility and thin-film processability, or in thin-film solids. These novel ligands preserve the discrete, size-dependent features of quantum confinement and enhance electronic coupling between the NCs in thin films.…”

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confidence: 99%

Flexible and low-voltage integrated circuits constructed from high-performance nanocrystal transistors

et al. 2012

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Colloidal semiconductor nanocrystals are emerging as a new class of solution-processable materials for low-cost, flexible, thin-film electronics. Although these colloidal inks have been shown to form single, thin-film field-effect transistors with impressive characteristics, the use of multiple high-performance nanocrystal field-effect transistors in large-area integrated circuits has not been shown. This is needed to understand and demonstrate the applicability of these discrete nanocrystal field-effect transistors for advanced electronic technologies. Here we report solution-deposited nanocrystal integrated circuits, showing nanocrystal integrated circuit inverters, amplifiers and ring oscillators, constructed from highperformance, low-voltage, low-hysteresis CdSe nanocrystal field-effect transistors with electron mobilities of up to 22 cm 2 V À 1 s À 1 , current modulation 410 6 and subthreshold swing of 0.28 Vdec À 1 . We fabricated the nanocrystal field-effect transistors and nanocrystal integrated circuits from colloidal inks on flexible plastic substrates and scaled the devices to operate at low voltages. We demonstrate that colloidal nanocrystal field-effect transistors can be used as building blocks to construct complex integrated circuits, promising a viable material for low-cost, flexible, large-area electronics.

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Exceptionally Mild Reactive Stripping of Native Ligands from Nanocrystal Surfaces by Using Meerwein’s Salt

Cited by 261 publications

References 53 publications

Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

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

Flexible and low-voltage integrated circuits constructed from high-performance nanocrystal transistors

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Exceptionally Mild Reactive Stripping of Native Ligands from Nanocrystal Surfaces by Using Meerwein’s Salt

Cited by 261 publications

References 53 publications

Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

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

Flexible and low-voltage integrated circuits constructed from high-performance nanocrystal transistors

Contact Info

Product

Resources

About

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