Size, Ligand, and Defect-Dependent Electron–Phonon Coupling in Chalcogenide and Perovskite Nanocrystals and Its Impact on Luminescence Line Widths,ACS Photonics

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Size, Ligand, and Defect-Dependent Electron–Phonon Coupling in Chalcogenide and Perovskite Nanocrystals and Its Impact on Luminescence Line Widths
ACS Photonics ( IF 6.5 ) Pub Date : 2020-04-01 , DOI: 10.1021/acsphotonics.0c00034
Nuri Yazdani ₁ , Sebastian Volk ₁ , Olesya Yarema ₁ , Maksym Yarema ₁ , Vanessa Wood ₁

Affiliation

The systematic study of electron–phonon coupling in nanocrystals (NC) via first-principles methods has been limited by the large system sizes presented by the NCs. Here, we present a method to extract electron–phonon coupling strengths from ab initio Molecular Dynamics simulations that is computationally less demanding. We use this method to investigate how electron–phonon coupling strengths depend on NC size, ligands, and defects for the model system of PbS NCs and also demonstrate its general applicability by leveraging the approach to compute electron–phonon coupling strengths in CdSe and CsPbI₃ NCs. The strong coupling of phonons to interband transitions in all NCs imposes fundamental limits to emission line widths. Our results indicate that coupling to localized vibrations stemming from undercoordinated atoms on the surface of the NCs contribute significantly to line width broadening and help to explain the experimentally observed trend that homogeneous line widths decrease with increasing NC size. Finally, we also demonstrate that mild surface defects on the NCs, which do not impact the ground state electronic structure of the NC, can dramatically increase radiative line widths.

中文翻译：

硫族化物和钙钛矿纳米晶体中的尺寸，配体和依赖缺陷的电子-声子耦合及其对发光线宽的影响

通过第一性原理方法对纳米晶体（NC）中的电子-声子耦合进行系统研究受到了NCs提出的大型系统的限制。在这里，我们提出了一种从头算分子动力学模拟中提取电子-声子耦合强度的方法，该方法在计算上要求不高。我们使用这种方法来研究电子-声子耦合强度如何取决于PbS NCs模型系统的NC尺寸，配体和缺陷，并通过利用计算CdSe和CsPbI _3中的电子-声子耦合强度的方法来证明其一般适用性。NCs。在所有NC中，声子与带间跃迁之间的强耦合对发射线宽度施加了基本限制。我们的结果表明，耦合到NC表面上未配位的原子引起的局部振动，显着有助于线宽加宽，并有助于解释实验观察到的趋势：均匀线宽随NC尺寸的增加而减小。最后，我们还证明了NC上的轻微表面缺陷（不会影响NC的基态电子结构）会大大增加辐射线宽。

更新日期：2020-04-01

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