Syntheses and photophysical properties of type-II CdSe/ZnTe/ZnS (core/shell/shell) quantum dots

Cheng, Colin C.J.; Chen, Chun‐Yen; Lai, Chih‐Wei; Liu, Wei-Hsin; Pu, Shih‐Chieh; Chou, Pi‐Tai; Chou, Yao-Hsin; Chiu, Hsin‐Tien

doi:10.1039/b503681j

Cited by 61 publications

(38 citation statements)

References 18 publications

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“…To develop an understanding of the role of the barrierw idth and shell thickness on the chargec arriers or excitons in the core/barrier/shell heterostructures, theoretical calculations based on EMA have been carriedo ut. [32] For this purpose, it was assumed that ac ore-shell NC is spherically symmetrical, havingC dSe as the core, CdS as the outer shell, and ZnSe as an intermediate layer between the CdSe and CdS. The values of the material properties are given in Table 2, where E g,bulk , m* e ,a nd m* h stand for the band gap of bulk semiconductor,e ffective mass of th eelectron, and effective mass of th ehole, respectively .Calculations were performed for various thicknesses of the barrier and shell.F or that purpose, the average thicknesseso fo ne ML of ZnSe and one ML of CdS were taken as 0.33 and 0.35 nm, respectively.…”

Section: Resultsmentioning

confidence: 99%

Thickness‐Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures

2015

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We report the synthesis of CdSe/ZnSe/CdS heterostructures composed of type I and type II band alignments, where ZnSe acts as a barrier for charge carriers between the CdSe core and the CdS shell as well as being an active component of the type I (CdSe/ZnSe) and type II (ZnSe/CdS) structure simultaneously. We investigated the effect of the thickness of the barrier and the shell on the charge carrier dynamics by using UV/Vis absorbance, photoluminescence (PL), and time-resolved fluorescence techniques. The experimental data are supported by simple theoretical calculations based on effective mass approximation (EMA). PL results indicate the emission from both type I and type II structures. Time-resolved fluorescence studies show that the lifetime of the core emission decreases with increasing barrier width, owing to a greater confinement of the exciton to the core, whereas it increases with shell width because of the tunneling of charge carriers, primarily electrons, delaying the recombination of the exciton. The lifetime of the shell emission decreases with shell width as well as barrier width and height, with a larger effect being observed for the barrier width and negligible for the associated changes in the barrier height.

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Section: Resultsmentioning

confidence: 99%

Thickness‐Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures

2015

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“…Originally, the construction of epitaxial core@shell structures was served to prepare core@shell quantum dots (QDs) with inorganic passivating shells to enhance the photoluminescence (PL) quantum yields. Till now, numerous epitaxial core@shell and core@multi-shell nanostructures made of group II-VI, IV-VI, and III-V semiconductors, such as CdSe@CdS [20,[47][48][49], CdS@ZnS [50][51][52][53], InP@ZnS [54][55][56][57], PbSe@PbS [58][59][60][61], PbSe@CdSe [62][63][64], ZnTe@CdSe [65][66][67], and CdSe@ZnTe-ZnS [68][69][70], have been prepared to enhance the PL, improve the stability, and tune the emission wavelength. The basic properties of different types of core@shell and core@multi-shell nanostructures with different chemical compositions and band alignment structures have been well summarized in several recent reviews [71][72][73].…”

Section: Core@shell Nanostructuresmentioning

confidence: 99%

Wet-Chemical Synthesis and Applications of Semiconductor Nanomaterial-Based Epitaxial Heterostructures

Chen

et al. 2019

Nano-Micro Lett.

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HIGHLIGHTS• The synthesis of semiconductor nanomaterial-based epitaxial heterostructures by wet-chemical methods is introduced. Various architectures based on different kinds of seeds or templates are illustrated, and their growth mechanisms are discussed in detail.• The applications of epitaxial heterostructures in optoelectronics, thermoelectrics, and catalysis are discussed. ABSTRACTSemiconductor nanomaterial-based epitaxial heterostructures with precisely controlled compositions and morphologies are of great importance for various applications in optoelectronics, thermoelectrics, and catalysis. Until now, various kinds of epitaxial heterostructures have been constructed. In this minireview, we will first introduce the synthesis of semiconductor nanomaterial-based epitaxial heterostructures by wet-chemical methods. Various architectures based on different kinds of seeds or templates are illustrated, and their growth mechanisms are discussed in detail. Then, the applications of epitaxial heterostructures in optoelectronics, catalysis, and thermoelectrics are described. Finally, we provide some challenges and personal perspectives for the future research directions of semiconductor nanomaterial-based epitaxial heterostructures. C ata lys is L i g h te m it ti ng dev ic e P h o t o v ol taic de v ic e T h e r m al elect ic d e v i c e Semiconductor Epitaxial Heterostructuressolution containing Cd-oleate [33]. The thermal decomposition of (NH 4 ) 2 MoS 4 or (NH 4 ) 2 WS 4 not only provided the sulfur source for the nucleation and growth of CdS seeds, but also acted as the precursor which decomposed to form MoS 2 or WS 2 nanosheets (NSs). Hydro-/Solvothermal StrategyEpitaxial heterostructures can also be prepared by the hydro-/solvothermal strategy, a typical wet-chemical synthesis method, which uses water or organic solvents as the reaction medium in a sealed steel pressure reactor with Teflon liner. The chemical reaction can proceed at the temperature higher than the boiling point of the solvent. Under such condition, high pressure can be generated, promoting the reaction and improving the crystallinity of the synthesized NCs [34]. The main advantage of the hydro-/solvothermal strategy is that almost all precursors can dissolve in the solvent at high pressure and temperature. Besides that, the merits of hydro-/solvothermal strategy, including the easy operability, high yield, and low cost, make it an attractive choice for constructing epitaxial heterostructures. As a typical example, Wang et al. reported the epitaxial growth of α-Fe 2 O 3 on CdS nanowires (NWs) via a two-step solvothermal process using N,N-dimethylformamide as solvent and poly(vinylpyrrolidone) as surfactant [35].Even though hydro-/solvothermal strategy has been widely used to prepare epitaxial heterostructures, it has disadvantages as well. Firstly, it is impossible to observe the reaction process in situ since the reaction occurs in a sealed autoclave, making it difficult to propose the growth mechanism. Besides, since the hydro-/solvothermal r...

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“…19 Additionally, the first boundary on the left side of a potential structure is defined here as the origin of the x-direction, and the external field is applied in a positive x-direction. The band gaps of CdSe and ZnS are 1.7 and 3.6 eV, respectively.…”

Section: Tilt Deformationmentioning

confidence: 99%

Experimental and theoretical study of localization of electrons by deformed potential well in quantum dots

2014

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The deformed potential structure of CdSe/ZnS core/shell quantum dots (QDs) was analyzed by calculating precise state energies and state functions. Exactly how an external electric field affects the photoluminescence was also studied. Additionally, the tilt potential structure induced by the external electric field, commonly referred to as the quantum-confined Stark effect, was calculated to account for the observed blue and red shifts. Experimental results indicated that the deformation also includes a bend, which is attributed to the shape of a QD. Calculations of the localization of electrons of the foregoing phenomena closely correspond to the experimental data.

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Syntheses and photophysical properties of type-II CdSe/ZnTe/ZnS (core/shell/shell) quantum dots

Cited by 61 publications

References 18 publications

Thickness‐Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures

Thickness‐Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures

Wet-Chemical Synthesis and Applications of Semiconductor Nanomaterial-Based Epitaxial Heterostructures

Experimental and theoretical study of localization of electrons by deformed potential well in quantum dots

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