Tuning band offsets of core/shell CdS/CdTe nanocrystals.

Abstract

The formation of multicomponent heterostructures has made semiconductor nanocrystals (NCs) attractive for engineering electronic and optical properties because of their ability to tune their band offsets at the interface. As is well known for bulk semiconductors, heterostructured semiconductor interfaces form at least two kinds of steplike electronic alignments. In the first situation, referred to as type I, photoexcited carriers are confined in the same space. Type-I heterojunction semiconductor NCs with ‘‘core/shell’’ geometries have been preferentially investigated for achieving high photoluminescence (PL) quantum yields. On the other hand, the type-II heterostructure spatially separates thephotoexcited electron andhole into different semiconductor components. Recently, type-II NCs have attracted growing attention because of potential uses for lasers andphotovoltaic technologies.Conventional strategies to tune the band offset relied mainly on definite choices of semiconductormaterials, following ananalogyof the bulk materials. For example, CdS/ZnSe and CdSe/ CdTe have often been used for type-II materials. In pioneering work, Klimov and co-workers have recently mentioned quasi-type-II transition of ZnSe/CdSe NCs, in which only holes are delocalized within a whole crystal for a specific shell thickness. However, in spite of the advanced studies, it is not entirely clear how to tune and manipulate the band offsets of heterostructured semiconductor nanosystems. There still remains the open question of whether size-tunable band potential, which derives from the quantum confinement effect, contributes to band-offset structures. In particular, the CdTe/CdS combination makes a quasi-type-II band alignment for bulk semiconductor analogy (Figure 1A), but few quasi-type-II CdTe/CdS nanomaterials have been reported. Herein, we focus on the synthesis, characterization, and tuningof bandoffsets of core/shellCdS/CdTeNCs.Wedesign a

DOI: 10.1002/smll.200900571

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Cite this paper

@article{Nonoguchi2009TuningBO, title={Tuning band offsets of core/shell CdS/CdTe nanocrystals.}, author={Yoshiyuki Nonoguchi and Takuya Nakashima and Tsuyoshi Kawai}, journal={Small}, year={2009}, volume={5 21}, pages={2403-6} }