Direct Synthesis of Six-Monolayer (1.9 nm) Thick Zinc-Blende CdSe Nanoplatelets Emitting at 585 nm

Cho, Wooje; Kim, Siyoung; Coropceanu, Igor; Srivastava, Vishwas; Diroll, Benjamin T.; Hazarika, Abhijit; Fedin, Igor; Galli, Giulia; Schaller, Richard D.; Talapin, Dmitri V.

doi:10.1021/acs.chemmater.8b02489

Cited by 86 publications

(140 citation statements)

References 32 publications

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“…The synthesis of CdSe NPLs is well established for NCs with two to eight monolayer (ML) thickness that emit at defined wavelengths in the visible range 2a,5a,e. Additional control on the lateral size of the NPLs enables a fine tuning of the emission wavelength around these values 5f.…”

Section: Resultssupporting

confidence: 77%

“…Controlling their shape and size is paramount to tune their optoelectronic properties and to achieve high photoluminescence quantum yield (PLQY) along with narrow and tunable emission . Through different synthetic strategies there is now access to a large variety of structures, from single material quantum dots, nanorods, and nanoplatelets (NPLs)2a,5 to core/shell systems that provide increased stability and photoluminescence efficiency, multifunctional particles that combine metallic and semiconductor portions, and highly sophisticated morphologies, such as branched and hollow NCs . This wealth in structural and material design translates into a broad range of applications in light emission, energy conversion, catalysis, and medicine 1b,10…”

Section: Introductionmentioning

confidence: 99%

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Core/Shell CdSe/CdS Bone‐Shaped Nanocrystals with a Thick and Anisotropic Shell as Optical Emitters

Castelli

Dhanabalan

Polovitsyn

et al. 2019

Advanced Optical Materials

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Colloidal core/shell nanocrystals are key materials for optoelectronics, enabling control over essential properties via precise engineering of the shape, thickness, and crystal structure of their shell. Here, the growth protocol for CdS branched nanocrystals is applied on CdSe nanoplatelet seeds and bone‐shaped heterostructures are obtained with a highly anisotropic shell. Surprisingly, the nanoplatelets withstand the high growth temperature of 350 °C and structures with a CdSe nanoplatelet core that is overcoated by a shell of cubic CdS are obtained, on top of which tetrahedral CdS structures with hexagonal lattice are formed. These complex core/shell nanocrystals show a band‐edge emission around 657 nm with a photoluminescence quantum yield of ≈42% in solution, which is also retained in thin films. Interestingly, the nanocrystals manifest simultaneous red and green emission and the relatively long wavelength of the green emission indicates charge recombination at the cubic/hexagonal interface of the CdS shell. The nanocrystal films show amplified spontaneous emission, random lasing, and distributed feedback lasing when the material is deposited on suitable gratings. This work stimulates the design and fabrication of more exotic core/shell heterostructures where charge carrier delocalization, dipole moment, and other optical and electrical properties can be engineered.

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Section: Resultssupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Core/Shell CdSe/CdS Bone‐Shaped Nanocrystals with a Thick and Anisotropic Shell as Optical Emitters

Castelli

Dhanabalan

Polovitsyn

et al. 2019

Advanced Optical Materials

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“…The intensity averaged lifetime of the PL emission at the bandedge (405 nm) is around 0.16 and 0.27 ns for the sample synthesized with excess Se and excess Cd, respectively. These measured PL lifetimes are significantly shorter than the previously reported PL decay lifetimes of 1–4 ns for 4ML and 5ML CdSe NPLs, which can be attributed to the significantly strong and fast carrier trapping in these subnanometer thick NPLs. We associate the two shorter lifetimes, Τ 1 ≈ 80–120 ps and Τ 2 ≈ 300 ps, to the trapping of the carriers and the longer component having a lifetime around 0.6 ns to the recombination of excitons at the bandedge .…”

Section: Resultsmentioning

confidence: 99%

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Delikanlı

Yeltik

et al. 2019

Adv Funct Materials

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Surface effects in atomically flat colloidal CdSe nanoplatelets (NLPs) are significantly and increasingly important with their thickness being reduced to subnanometer level, generating strong surface related deep trap photoluminescence emission alongside the bandedge emission. Herein, colloidal synthesis of highly luminescent two-monolayer (2ML) CdSe NPLs and a systematic investigation of carrier dynamics in these NPLs exhibiting broad photoluminescence emission covering the visible region with quantum yields reaching 90% in solution and 85% in a polymer matrix is shown. The astonishingly efficient Stokes-shifted broadband photoluminescence (PL) emission with a lifetime of ≈100 ns and the extremely short PL lifetime of around 0.16 ns at the bandedge signify the participation of radiative midgap surface centers in the recombination process associated with the underpassivated Se sites. Also, a proof-of-concept hybrid LED employing 2ML CdSe NPLs is developed as color converters, which exhibits luminous efficacy reaching 300 lm W opt −1 . The intrinsic absorption of the 2ML CdSe NPLs (≈2.15 × 10 6 cm −1 ) reported in this study is significantly larger than that of CdSe quantum dots (≈2.8 × 10 5 cm −1 ) at their first exciton signifying the presence of giant oscillator strength and hence making them favorable candidates for next-generation light-emitting and light-harvesting applications.

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“…25 Halide are X-type 26 ligands, and they have also been grafted onto NPL surfaces to control the PL yield or NPL shape 27,28 or to serve as ripening agents to grow thicker NPLs. 29,30 In this article, we demonstrate the exchange of native carboxylate ligands by halide ligands that are costabilized by a primary amine due to hydrogen bonding on cadmium chalcogenide NPLs. This exchange leads to an increase in the fluorescence efficiency (up to 70% in toluene) for core-only NPLs.…”

mentioning

confidence: 94%

Halide Ligands To Release Strain in Cadmium Chalcogenide Nanoplatelets and Achieve High Brightness

et al. 2019

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Zinc blende II-VI semiconductor nanoplatelets (NPLs) are defined at the atomic scale along the thickness of the nanoparticle and are initially capped with carboxylates on the top and bottom [001] facets. These ligands are exchanged on CdSe NPLs with halides that act as X-L-type ligands. These CdSe NPLs are costabilized by amines to provide colloidal stability in nonpolar solvents. The hydrogen from the amine can participate in a hydrogen bond with the lone pair electrons of surface halides. After ligand exchange, the optical features are redshifted. Thus, ligand tuning is another way, in addition to confinement, to tune the optical features of NPLs. The improved surface passivation leads to an increase in the fluorescence quantum efficiency of up to 70% in the case of bromide. However, for chloride and iodide, the surface coverage is incomplete, and thus, the fluorescence quantum efficiency is lower. This ligand exchange is associated with a decrease in stress that leads to unfolding of the NPLs, which is particularly noticeable for iodide-capped NPLs.

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Direct Synthesis of Six-Monolayer (1.9 nm) Thick Zinc-Blende CdSe Nanoplatelets Emitting at 585 nm

Cited by 86 publications

References 32 publications

Core/Shell CdSe/CdS Bone‐Shaped Nanocrystals with a Thick and Anisotropic Shell as Optical Emitters

Core/Shell CdSe/CdS Bone‐Shaped Nanocrystals with a Thick and Anisotropic Shell as Optical Emitters

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Halide Ligands To Release Strain in Cadmium Chalcogenide Nanoplatelets and Achieve High Brightness

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