Type-II CdSe/CdTe Core/Crown Semiconductor Nanoplatelets

Pedetti, Silvia; Ithurria, Sandrine; Heuclin, Hadrien; Patriarche, G.; Dubertret, Benoît

doi:10.1021/ja509307m

Cited by 169 publications

(318 citation statements)

References 58 publications

(103 reference statements)

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“…34 Since our platelets have a relatively large lateral size and hence increased coherence volume, 34,47 the GOST effect also leads to shorter lifetimes compared to ref. 41. Due to relatively high PL quantum yield in our samples (23%) for the 5 ML CdSe-CdTe hetero-NPLs we can definitely exclude the idea that the observed fast exciton lifetimes in our type-II hetero-NPLs result from dominating non-radiative processes since τ dec = τ rad ·QY, so that the measured decay time τ dec cannot be considerably smaller than the radiative lifetime τ rad .…”

Section: Pl Lifetime Measurementsmentioning

confidence: 69%

“…Similar behaviour was observed earlier for 4 and 5 ML CdSe-CdTe hetero-NPLs prepared by different protocols. [41][42][43] The PL quantum yield of our 5 ML CdSe-CdTe HNPLs, measured at room temperature in chloroform relative to Rhodamine 6G in ethanol, was 23%. This is a rather high value for the HNCs with an indirect optical transition schematically shown in Fig.…”

Section: Resultsmentioning

confidence: 88%

“…by the growth of gradient structures. 41 It is interesting to compare the optical properties of the CdSe(core)-CdTe(wings) hetero-NPLs with the inverted CdTe (core)-CdSe(wings) structure. However, we failed to prepare 5 ML thick CdTe NPLs by following the protocol described in ref.…”

Section: Resultsmentioning

confidence: 99%

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Colloidal synthesis and optical properties of type-II CdSe–CdTe and inverted CdTe–CdSe core–wing heteronanoplatelets

et al. 2015

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We developed colloidal synthesis to investigate the structural and electronic properties of CdSe-CdTe and inverted CdTe-CdSe heteronanoplatelets and experimentally demonstrate that the overgrowth of cadmium selenide or cadmium telluride core nanoplatelets with counterpartner chalcogenide wings leads to type-II heteronanoplatelets with emission energies defined by the bandgaps of the CdSe and CdTe platelets and the characteristic band offsets. The observed conduction and valence band offsets of 0.36 eV and 0.56 eV are in line with theoretical predictions. The presented type-II heteronanoplatelets exhibit efficient spatially indirect radiative exciton recombination with a quantum yield as high as 23%.While the exciton lifetime is strongly prolonged in the investigated type-II 2D systems with respect to 2D type-I systems, the occurring 2D giant oscillator strength (GOST) effect still leads to a fast and efficient exciton recombination. This makes type-II heteronanoplatelets interesting candidates for low threshold lasing applications and photovoltaics.

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Section: Pl Lifetime Measurementsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 88%

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Colloidal synthesis and optical properties of type-II CdSe–CdTe and inverted CdTe–CdSe core–wing heteronanoplatelets

et al. 2015

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“…Also, it was shown that higher concentration of OA results in formation of extended CdTe crown region and enhances the absorption of crown region. 34 However, for the CdSe/CdTe core/crown NPLs synthesized by using an excess amount of TOP ( Figure S1 in the Supporting Information), the excitonic peak corresponding to 4 ML thick CdTe crown layer could not observed clearly, which can be attributed to the nonuniform and/or partial coating of CdTe crown region. Moreover, an absorption tail extending into the lower energy side of the absorption spectra is observed, and this can be attributed to the intermediate transitions at the core/crown interface owing to the Type-II band alignment.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Recently, during the review process of our work, the report by Pedetti et al appeared to show the synthesis and characterization of CdSe/ CdTe core/crown NPLs having Type-II electronic structure using a different cadmium precursor. 34 Here, in an independent study, we report the synthesis of CdSe/CdTe core/crown NPLs having Type-II electronic structure with varying crown width by using core-seeded lateral shell growth approach. With the laterally grown CdTe crown region, atomically flat CdSe/CdTe core/crown NPLs are achieved, which is highly promising for efficiently removal of excited carriers.…”

Section: ■ Introductionmentioning

confidence: 99%

Type-II Colloidal Quantum Wells: CdSe/CdTe Core/Crown Heteronanoplatelets

et al. 2015

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Solution-processed quantum wells, also known as colloidal nanoplatelets (NPLs), are emerging as promising materials for colloidal optoelectronics. In this work, we report the synthesis and characterization of CdSe/CdTe core/crown NPLs exhibiting a Type-II electronic structure and Type-II specific optical properties. Here, based on a core-seeded approach, the CdSe/CdTe core/crown NPLs were synthesized with well-controlled CdTe crown coatings. Uniform and epitaxial growth of CdTe crown region was verified by using structural characterization techniques including transmission electron microscopy (TEM) with quantitative EDX analysis and X-ray diffraction (XRD). Also the optical properties were systematically studied in these Type-II NPLs that reveal strongly red-shifted photoluminescence (up to ∼150 nm) along with 2 orders of magnitude longer fluorescence lifetimes (up to 190 ns) compared to the Type-I NPLs owing to spatially indirect excitons at the Type-II interface between the CdSe core and the CdTe crown regions. Photoluminescence excitation spectroscopy confirms that this strongly red-shifted emission actually arises from the CdSe/CdTe NPLs. In addition, temperature-dependent time-resolved fluorescence spectroscopy was performed to reveal the temperature-dependent fluorescence decay kinetics of the Type-II NPLs exhibiting interesting behavior. Also, water-soluble Type-II NPLs were achieved via ligand exchange of the CdSe/CdTe core/crown NPLs by using 3-mercaptopropionic acid (MPA), which allows for enhanced charge extraction efficiency owing to their shorter chain length and enables high quality film formation by layer-by-layer (LBL) assembly. With all of these appealing properties, the CdSe/CdTe core/crown heterostructures having Type-II electronic structure presented here are highly promising for light-harvesting applications.

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Colloidal Quantum‐Dot Heterostructures Studied Using Aberration‐Corrected Scanning Transmission Electron Microscopy

Patriarche¹,

Pantzas²,

Pedetti

et al. 2016

European Microscopy Congress 2016: Proceedings

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Complex colloidal semiconductor quantum‐ dot heterostructures, such as core/shell or core/crown nanoplatelets, can now be readily synthesized [1‐4]. Such heterostructures significantly enhance the optical properties of the colloidal quantum dots. The optical properties of these colloidal quantum dots depend not only on the morphology of the heterostructure – i.e. the size and shape of the core‐, but, more importantly on the chemical nature and the presence of a composition gradient at the heterostructure interfaces, and on the elastic deformation inside the quantum dots that is due to a lattice mismatch between the core and shell/crown materials. The study of these heterostructures through aberration‐corrected Scanning Transmission Electron Microscopy (STEM) provides access to their structure down to the atomic scale. High Angle Annular Dark Field STEM images, in particular, provide direct access to the atomic structure of the nanoparticles, and through the contrast of the atomic columns (“Z‐contrast” images) to their chemical nature. Therefore, atomic resolution STEM images allow one possible to precisely map the strain fields of the heterostructure. Finally, chemical information accessed through the Z‐contrast can be correlated to quantitative STEM‐EDX with a spatial resolution of 1 nm. The present talk summarizes such studies conducted on CdSe/Cd(Zn)S core/shell [1,2], and core/crown CdSe/CdS [3,4] and CdSe/CdTe nanoplatelets.

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Type-II CdSe/CdTe Core/Crown Semiconductor Nanoplatelets

Cited by 169 publications

References 58 publications

Colloidal synthesis and optical properties of type-II CdSe–CdTe and inverted CdTe–CdSe core–wing heteronanoplatelets

Colloidal synthesis and optical properties of type-II CdSe–CdTe and inverted CdTe–CdSe core–wing heteronanoplatelets

Type-II Colloidal Quantum Wells: CdSe/CdTe Core/Crown Heteronanoplatelets

Colloidal Quantum‐Dot Heterostructures Studied Using Aberration‐Corrected Scanning Transmission Electron Microscopy

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