CdSe/CdSe1–xTex Core/Crown Heteronanoplatelets: Tuning the Excitonic Properties without Changing the Thickness

Keleştemur, Yusuf; Güzeltürk, Burak; Erdem, Onur; Olutaş, Murat; Erdem, Talha; Usanmaz, Can Firat; Gungor, Kivanc; Demir, Hilmi Volkan

doi:10.1021/acs.jpcc.6b11809

Cited by 50 publications

(90 citation statements)

References 41 publications

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“…Chromaticity coordinates of the LED were calculated between (0.37, 0.54) and (0.35, 0.49) with increasing current from 50 to 350 mA (Figure 6c). The luminous efficacy of optical radiation (LER) of this LED reaches 300 lm W opt −1 as presented in Figure b, greatly surpassing the previous results from the LEDs utilizing NPLs and small QDs (2 nm < diameter) because of the strong overlap of the NPL emission with the human eye sensitivity function and the high QY of solid films of our NPLs. However, as can be seen in Figure b, the emission from the exciting LED at 380 nm leads to a reduction at high currents in the LER performance since it can be only weakly sensed by the human eye.…”

Section: Resultscontrasting

confidence: 51%

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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Section: Resultscontrasting

confidence: 51%

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Delikanlı

Yeltik

et al. 2019

Adv Funct Materials

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“…The exciton characteristics of the resulting CdSe x Te 1‒ x NPLs are redshifted and the PL linewidth is strongly broadened. Similarly undesirable behavior was reported by Demir and co‐workers for CdSe/CdSe x Te 1‒ x core/crown NPLs . On the other hand, alloying CdSe NPLs with sulfur leads to CdSe x S 1– x NPLs and a shift of the PL to the blue that maintains the narrow emission peak …”

Section: Introductionsupporting

confidence: 73%

Brightly Luminescent Core/Shell Nanoplatelets with Continuously Tunable Optical Properties

Meerbach

Tietze

Voigt

et al. 2019

Advanced Optical Materials

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A straightforward, rapid method to create colloidally stable and brightly luminescent core/shell CdSe‐based nanoplatelets (NPLs) with fluorescence quantum yields (QYs) up to 50% is demonstrated. A layer‐by‐layer deposition technique is used which is based on a two‐phase mixture—consisting of a nonpolar phase, which includes the NPLs, and a saturated ionic polar phase—to separate the reagents and hinder the nucleation of the shell material. The deposition of the first sulfur layer leads to a significant redshift (by more than 100 nm) of the optical absorption and emission of the NPLs. Hence, by varying either the sulfur precursor content or the reaction time, one can precisely and continuously tune the absorption and emission maxima from 520 to 630 nm. This evolution of the absorption onset during the shell growth is explained quantitatively using density‐functional theory and atomistic statistical simulations. The emission can be further enhanced by exposure of the NPL solution to ambient sunlight. Finally, it is demonstrated that the core/shell NPLs can be transferred from the organic solution to aqueous media with no reduction of their QY, which opens the door to a broad range of practical applications.

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“…Afterward, CdSe/ CdSe 1−x Te x core/alloyed-crown type-II NPLs with six different compositions (for x = 0.05, 0.10, 0.25, 0.40, 0.50, and 1.00) were synthesized according to our previously reported procedure with slight modifications. 27 To confirm successful syntheses, the compositions of the resulting core/alloyedcrown type-II NPLs were determined by X-ray photoelectron spectroscopy (XPS). The final Se and Te compositions of the alloyed crown (Table S1) were found to be well-controlled by the injected precursor amounts.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Highly Stable Multicrown Heterostructures of Type-II Nanoplatelets for Ultralow Threshold Optical Gain

et al. 2019

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Solution-processed type-II quantum wells exhibit outstanding optical properties, which make them promising candidates for light-generating applications including lasers and LEDs. However, they may suffer from poor colloidal stability under ambient conditions and show strong tendency to assemble into face-to-face stacks. In this work, to resolve the colloidal stability and uncontrolled stacking issues, we proposed and synthesized CdSe/CdSe 1−x Te x /CdS core/multicrown heteronanoplatelets (NPLs), controlling the amount of Te up to 50% in the crown without changing their thicknesses, which significantly increases their colloidal and photostability under ambient conditions and at the same time preserving their attractive optical properties. Confirming the final lateral growth of CdS sidewalls with X-ray photoelectron spectroscopy, energy-dispersive analysis, and photoelectron excitation spectroscopy, we found that the successful coating of this CdS crown around the periphery of conventional type-II NPLs prevents the unwanted formation of needle-like stacks, which results in reduction of the undesired scattering losses in thin-film samples of these NPLs. Owing to highly efficient exciton funneling from the outmost CdS crown accompanied by the reduced scattering and very low waveguide loss coefficient (∼18 cm −1), ultralow optical gain thresholds of multicrown type-II NPLs were achieved to be as low as 4.15 μJ/cm 2 and 2.48 mJ/cm 2 under one-and two-photon absorption pumping, respectively. These findings indicate that the strategy of using engineered advanced heterostructures of nanoplatelets provides solutions for improved colloidal stability and enables enhanced photonic performance.

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CdSe/CdSe_1–xTe_x Core/Crown Heteronanoplatelets: Tuning the Excitonic Properties without Changing the Thickness

Cited by 50 publications

References 41 publications

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Brightly Luminescent Core/Shell Nanoplatelets with Continuously Tunable Optical Properties

Highly Stable Multicrown Heterostructures of Type-II Nanoplatelets for Ultralow Threshold Optical Gain

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