Colloidal quantum-dot light-emitting diodes with metal-oxide charge transport layers

Caruge, Jean-Michel; Halpert, Jonathan E.; Wood, Vanessa; cacute, V. Bulovi; Bawendi, Moungi G.

doi:10.1038/nphoton.2008.34

Cited by 894 publications

(748 citation statements)

References 20 publications

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“…They enable bandgap tuning via adjustment of the nanoparticle size 1,2 . This has led to promising optoelectronic devices for lighting 3,4 , solar power conversion [5][6][7][8][9] and photon detection 10,11 . In solar cells, these materials have recently exceeded 7% certified power conversion efficiency (PCE) 5,12,13 , offering a promising path towards efficient, low-cost and roll-to-roll processed photovoltaics (PVs).…”

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confidence: 99%

Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

et al. 2014

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Colloidal quantum dots are attractive materials for efficient, low-cost and facile implementation of solution-processed optoelectronic devices. Despite impressive mobilities (1-30 cm 2 V À 1 s À 1 ) reported for new classes of quantum dot solids, it is-surprisingly-the much lower-mobility (10 À 3 -10 À 2 cm 2 V À 1 s À 1 ) solids that have produced the best photovoltaic performance. Here we show that it is not mobility, but instead the average spacing among recombination centres that governs the diffusion length of charges in today's quantum dot solids. In this regime, colloidal quantum dot films do not benefit from further improvements in charge carrier mobility. We develop a device model that accurately predicts the thickness dependence and diffusion length dependence of devices. Direct diffusion length measurements suggest the solid-state ligand exchange procedure as a potential origin of the detrimental recombination centres. We then present a novel avenue for in-solution passivation with tightly bound chlorothiols that retain passivation from solution to film, achieving an 8.5% power conversion efficiency.

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confidence: 99%

Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

et al. 2014

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“…The charge transport layers facilitate the extraction of carriers in photovoltaic devices and injection of carriers in light emitting devices. In the case of light emitting devices, the charge transport layers reduce the barrier to holes and electrons that are injected from the electrode into the QD emissive layer [2][3][4]. Suitable inorganic electron transport layers reported so far are zinc oxide, titanium dioxide, and tin oxide, which are intrinsically n-type materials [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

“…In the case of light emitting devices, the charge transport layers reduce the barrier to holes and electrons that are injected from the electrode into the QD emissive layer [2][3][4]. Suitable inorganic electron transport layers reported so far are zinc oxide, titanium dioxide, and tin oxide, which are intrinsically n-type materials [1][2][3][4]. The conduction band of the electron transport layers align with the conduction band of the QD and thereby reduce the barrier to electrons injected from the cathode, but there are not enough hole transport layers (HTLs) with suitable valence band alignment with the QDs.…”

Section: Introductionmentioning

confidence: 99%

“…The conduction band of the electron transport layers align with the conduction band of the QD and thereby reduce the barrier to electrons injected from the cathode, but there are not enough hole transport layers (HTLs) with suitable valence band alignment with the QDs. Even though some p-type materials are used as HTLs, the efficiency of the devices is much lower due to valence band mismatch [1,[2][3][4]. Non-stoichiometric nickel oxide (NiO) has been successfully employed as an HTL in quantum light emitting devices (QLEDs), but imbalance in the charge injection into the QDs created by the high barrier to holes resulted in low efficiency [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of charge transport between nickel oxide nanoparticles and CdSe/ZnS alloyed nanocrystals

et al. 2017

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Charge transport between nickel oxide nanoparticles and CdSe/ZnS alloyed core/shell nanocrystals is investigated. The crystal structure and composition of the nickel oxide nanoparticles are evaluated using X-ray diffraction, Raman and X-ray photoelectron spectroscopies. The nanoparticles are near-stoichiometric with very low defect densities. The optical properties of the materials are studied by measuring the absorbance and time resolved photoluminescence spectra. The band gap of the nickel oxide nanoparticles is around 4.42 eV. The CdSe/ZnS nanocrystals exhibit shorter average lifetimes when mixed with nickel oxide nanoparticle powder. The lifetime quenching can be attributed to the efficient charge transport from the CdSe/ZnS nanocrystals to nickel oxide nanoparticles due to the relative valence band alignment.

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“…[1][2][3] As the technologies for fabricating GaN-based LEDs and for synthesizing semiconductor colloidal nanocrystals (NQDs) mature, hybrid NQD-GaN LEDs are becoming promising candidates for highly efficient multi-color lighting. The high quantum yield and photostability of colloidal NQDs offer the possibility for flexible, low cost, large area, and simply-processed optoelectronic devices, while their emission color can be tuned from the visible to the near infrared range by either changing their size or chemical composition.…”

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confidence: 99%

Increased Color‐Conversion Efficiency in Hybrid Light‐Emitting Diodes utilizing Non‐Radiative Energy Transfer

et al. 2010

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There have been numerous efforts to increase the efficiency of solid-state lighting, lightemitting diodes (LEDs) and displays during the last decades. [1][2][3] As the technologies for fabricating GaN-based LEDs and for synthesizing semiconductor colloidal nanocrystals (NQDs) mature, hybrid NQD-GaN LEDs are becoming promising candidates for highly efficient multi-color lighting. The high quantum yield and photostability of colloidal NQDs offer the possibility for flexible, low cost, large area, and simply-processed optoelectronic devices, while their emission color can be tuned from the visible to the near infrared range by either changing their size or chemical composition. [4] Also the epitaxial growth of GaN has now reached the stage where GaN-based LEDs have an internal quantum efficiency of 80%. [5] Although their external quantum efficiency is inevitably limited by total internal reflection due to the high refractive index contrast with air, several approaches to improve the outcoupling efficiency have been realised implementing smart photonic crystal and waveguide designs. [6,7] Color conversion LEDs consisting of colloidal NQD emitters pumped by GaNbased LEDs overcome the drawback of NQDs, i.e. low carrier transfer. [8] A thin NQD layer deposited on LED surface absorbs the high energy photons that are electrically generated in the LED and subsequently reemits lower energy photons. As a result, there is no charge transfer among colloidal NQDs involved in this color conversion process. However, the efficiency of radiative energy transfer is relatively low, <10%, due to several energy loss steps in the transfer process, i.e. waveguided leaky mode losses, light scattering from the NQDs and

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Colloidal quantum-dot light-emitting diodes with metal-oxide charge transport layers

Cited by 894 publications

References 20 publications

Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

Investigation of charge transport between nickel oxide nanoparticles and CdSe/ZnS alloyed nanocrystals

Increased Color‐Conversion Efficiency in Hybrid Light‐Emitting Diodes utilizing Non‐Radiative Energy Transfer

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