Controlling Charge Carrier Overlap in Type-II ZnSe/ZnS/CdS Core鈥揃arrier鈥揝hell Quantum Dots

详细信息    查看全文

• 作者：Klaus Boldt ; Charusheela Ramanan ; Alina Chanaewa ; Matthias Werheid ; Alexander Eychm眉ller
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：6
• 期：13
• 页码：2590-2597
• 全文大小：523K
• ISSN：1948-7185

文摘

We describe the synthesis and spectroscopic characterization of colloidal ZnSe/ZnS/CdS nanocrystals, which exhibit a type-II electronic structure and wave function overlap that is strongly dependent on the thickness of the ZnS barrier. Barrier thickness is controlled by both the amount of deposited material and the reaction and annealing temperature of CdS shell growth. The results show that a single monolayer of ZnS mitigates the overlap significantly, while four and more monolayers effectively suppress band edge absorption and emission. Transient absorption spectra reveal a broad distribution of excitons with mixed S and P symmetry, which become allowed due to alloy formation and contribute to charge carrier relaxation across the barrier. We present a model of the core/shell interface based on cation diffusion, which allows one to estimate the extent of the diffusion layer from optical spectra.