多型性对CdSe / CdS和CdSe / CdSe核/壳纳米晶体电子结构的影响,The Journal of Physical Chemistry C

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多型性对CdSe / CdS和CdSe / CdSe核/壳纳米晶体电子结构的影响
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-03-13 00:00:00 , DOI: 10.1021/acs.jpcc.7b00778
Carlos Segarra ₁ , Fernando Rajadell ₁ , Juan I. Climente ₁ , Josep Planelles ₁

Affiliation

我们解决CdSe / CdS点状纳米晶体（NCs）与纤锌矿/纤锌矿（WZ / WZ），闪锌矿/锌闪锌矿（ZB / ZB）和多型ZB / WZ的电子结构的理论差异和相似性晶相，因为它们目前正在合成并用于光电器件。我们显示，在量子限制和应变方面，多型CdSe / CdS NCs的电子结构与WZ或ZB NCs的电子结构非常相似，从而产生相似的单激子波函数。主要区别在于内置电场的性质和大小。我们预测，由于立方核和六角形壳晶格之间的强烈自发极化失配，这些字段在多型中比纯WZ或ZB NC中更强。目前认为NCs中的极化可以通过几种表面效应来屏蔽。但是，在多型结构中，界面处的极化失配可能会产生有效电荷，该电荷与要淬灭的外表面足够远。为了对这个有争议的问题做出确定的评估，我们建议在多型ZB / WZ NC中进行实验，其中核壳均由CdSe制成。在这种情况下，带隙很小，不存在应变，我们的计算预测热电应成为驱动力，并随着核或壳尺寸的增加而引起从I型激子到II型激子的转变。为了对这个有争议的问题做出确定的评估，我们建议在多型ZB / WZ NC中进行实验，其中核壳均由CdSe制成。在这种情况下，带隙很小，不存在应变，我们的计算预测热电应成为驱动力，并随着核或壳尺寸的增加而引起从I型激子到II型激子的转变。为了对这个有争议的问题做出确定的评估，我们建议在多型ZB / WZ NC中进行实验，其中核壳均由CdSe制成。在这种情况下，带隙很小，不存在应变，我们的计算预测热电应成为驱动力，并随着核或壳尺寸的增加而引起从I型激子到II型激子的转变。

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Influence of Polytypism on the Electronic Structure of CdSe/CdS and CdSe/CdSe Core/Shell Nanocrystals

We address theoretically differences and similarities on the electronic structure of CdSe/CdS dot-in-dot nanocrystals (NCs) with wurtzite/wurtzite (WZ/WZ), zinc-blende/zinc-blende (ZB/ZB) and polytype ZB/WZ crystalline phases, as they are currently being synthesized and used in optoelectronic devices. We show that the electronic structure of polytypic CdSe/CdS NCs closely resembles that of WZ or ZB NCs with regard to quantum confinement and strain, resulting in similar single-exciton wave functions. The main differences arise in the nature and magnitude of built-in electric fields. We predict that these fields are stronger in polytypes than in pure WZ or ZB NCs due to the sharp spontaneous polarization mismatch between the cubic core and the hexagonal shell lattices. Polarization in NCs is currently believed to be screened by several surface effects. In polytypical structures, however, the polarization mismatch at the interface may create effective charges that are sufficiently far from the outer surface to be quenched. To make a definitive assessment on this controversial issue, we propose experiments in polytypic ZB/WZ NCs where both core and shell are made of CdSe. In such a case, band offsets are small, strain is absent, and our calculations predict pyroelectricity should become the driving force, inducing transitions from type-I to type-II excitons with increasing core or shell size.

更新日期：2017-03-13

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