Synthesis, Characterization, and Spectroscopy of Type‐II Core/Shell Semiconductor Nanocrystals with ZnTe Cores

Abstract

Type‐II core/shell quantum dots are characterized by a staggered alignment of conduction and valence bands (see Figure), giving rise to a broad tunability of absorption and emission wavelengths. Colloidal ZnTe/CdE (E = S, Se, Te) core/shell quantum dots have been prepared with emission quantum yields of up to 30 %. The synthesis route presented should be applicable to other type‐II core/shell quantum dots.

Aqueous phase synthesis and fluorescence properties of inverted core/shell ZnSe/CdSe nanocrystals

“…2(b)). This is due to the small lattice mismatch derived from the zinc-blende modifications of ZnSe and CdSe, similar to previous literature [29] . Besides, the diffraction peaks become narrower.…”

Preparation of Highly Luminescent CdTe/CdS Core/Shell Quantum Dots

“…[32], since all the samples show a sharp first excitonic absorption onset (see Figure 1 A), which is distinctly different from the featureless sub-bandgap absorption tail indicative of the spatially indirect transitions expected for a type-II core/shell structure. [48,49] Furthermore, the fact that the PL QYs of the formed core/shell structures increase steadily upon overcoating with the CdS shell material also supports the ascription of a type-I structure because the type-II core/shell structure usually leads to a decline of the PL QY. While the observation that the maximum red shift achieved in our experiment is around 121 nm when comparing the 2.6 nm plain CdTe core with the core coated with a 5-ML CdS shell supports the ascription of type-II structure since a longer emission wavelength could be accessed in the type-II structure.…”

“…While the observation that the maximum red shift achieved in our experiment is around 121 nm when comparing the 2.6 nm plain CdTe core with the core coated with a 5-ML CdS shell supports the ascription of type-II structure since a longer emission wavelength could be accessed in the type-II structure. [48,49] This should be the largest red-shifted value observed in the CdTe/CdS system. [25][26][27][28][29][30][31][32] The less red-shifted values observed in previous reports may be due to different reasons: 1) the CdS layer is a gradient layer with a CdTe concentration gradient that decreases towards the surface, as observed in aqueous-media synthesis; [25][26][27][28] 2) the CdS thickness is much smaller than expected.…”

One‐Pot Synthesis of Dual‐Stabilizer‐Capped CdTe Nanocrystals with Efficient Near‐Infrared Photoluminescence and Electrochemiluminescence

“…[7][8][9] CdTe is an important small-band-gap material, and water-soluble visible-emitting CdTe NCs have been extensively prepared in aqueous media. [2] Because type-II NCs can demonstrate a longer PL wavelength than any of the single materials, [10,11] a large amount of aqueous synthetic methods have been carried out for type-II CdTe NCs including CdTe-based core/shell systems, [10] or alloys. [12] Although several type-II NIR-emitting CdTe NCs, such as CdTe/CdS, [13] CdTe/CdSe, [14] CdTe/ZnS, [15] CdHgTe, [16] and CdHgTe/CdS [17] have been synthesized, this strategy is still extremely challenging.…”