Institute for Molecular Engineering, The University of Chicago , 5640 South Ellis Avenue, Chicago, Illinois 60637, United States.
Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
Nano Lett. 2017 Apr 12;17(4):2547-2553. doi: 10.1021/acs.nanolett.7b00283. Epub 2017 Mar 23.
Heterogeneous nanostructures, such as quantum dots (QDs) embedded in solid matrices or core-shell nanoparticles, are promising platforms for a wide variety of applications, including phosphors with increased quantum yield, photocatalysis, and solar energy conversion. However, characterizing and controlling their interfacial morphology and defects, which greatly influence their electronic properties, have proven difficult in numerous cases. Here we carried out atomistic calculations on chalcogenide nanostructured materials, i.e., PbSe QDs in CdSe matrices and CdSe embedded in PbSe, and we established how interfacial and core structures affect their electronic properties. In particular, we showed that defects present at interfaces of PbSe nanoparticles and CdSe matrices give rise to detrimental intragap states, degrading the performance of photovoltaic devices. Instead, the electronic gaps of the inverted system (CdSe dots in PbSe) are clean, indicating that this material has superior electronic properties for solar applications. In addition, our calculations predicted that the core structure of CdSe and in turn its band gap may be tuned by applying pressure to the PbSe matrix, providing a means to engineering the properties of new functional materials.
杂化纳米结构，如嵌入在固体基质中的量子点（QD）或核壳纳米粒子，是在各种应用中具有广阔前景的平台，包括量子产率增加的荧光粉、光催化和太阳能转换。然而，在许多情况下，表征和控制它们的界面形态和缺陷，这极大地影响了它们的电子性质，是具有挑战性的。在这里，我们对硫属化物纳米结构材料进行了原子级计算，即 PbSe QD 在 CdSe 基质中以及 CdSe 嵌入 PbSe 中的情况，并确定了界面和核结构如何影响它们的电子性质。具体来说，我们表明，PbSe 纳米粒子和 CdSe 基质界面处的缺陷会导致有害的带隙内态，从而降低光伏器件的性能。相比之下，颠倒体系（CdSe 点在 PbSe 中）的能隙是干净的，这表明这种材料在太阳能应用方面具有更好的电子性质。此外，我们的计算预测，通过对 PbSe 基质施加压力，可以调整 CdSe 的核结构，从而改变其能带隙，为新型功能材料的性质调控提供了一种手段。
