Band Alignment Engineering of Semiconductor Nanocrystal Heterostructures Toward Emerging Applications

Abstract

Due to the superb tunable properties of quantum dots (QDs), they have been largely studied in the past few decades for many promising applications. However, for a single nanocrystal QD, its properties are largely limited due to limited tunability of the composition, charge carrier dynamics, band alignment, and so on. Thus, to solve the problem, and enhance their physical, chemical, electrical, and optical properties, the heterostructure nanocrystals (NCs), which combine single NCs with other materials of either semiconductor or metal, are proposed. In these heterostructures, their properties can be modified through tailoring the band alignment, and therefore providing a great potential for widespread applications. Here, an overview of strategies for band alignment engineering, synthesis methods, and the corresponding applications, such as lighting devices, lasers, photocatalysis, biological applications are offered.

Anisotropic Heavy-Metal-Free Semiconductor Nanocrystals: Synthesis, Properties, and Applications

“…Hence, heavy-metal-free semiconductor NCs are considered as promising alternatives to those containing heavy-metal ions, due to the low toxicity and comparable optical and electrical properties and show great potential in various applications. Semiconductor NCs are nanomaterials whose dimension in any direction is similar to or smaller than their Bohr radius, in which the excitons are confined due to the quantum confinement effect, thus resulting in unique properties, such as size-dependent band gaps, discrete energy levels, tunable surface chemistry, tunable charge transport and so on. − Depending on which dimension the excitons are confined, semiconductor NCs can be divided into two categories, including isotropic zero-dimensional (0D) spherical quantum dots (QDs) with the excitons being confined on all dimensions and anisotropic one-dimensional (1D) and two-dimensional (2D) NCs with the excitons being confined on two dimensions and one dimension, respectively. − In this review, we treated both morphology anisotropic and composition anisotropic NCs as anisotropic NCs. Morphology anisotropic NCs include 1D NCs (nanorods (NRs), nanowires (NWs), nanotubes, and so on), − 2D nanoplatelets (NPLs), nanosheets and so on), − and other morphologies such as branched structures − and nanocubes. − Composition anisotropic NCs consist of heterostructures based on anisotropic shape, which means that the core/shell quantum dots (QDs) are not included in this review, since we considered that these core/shell QDs still possess symmetrical structure.…”