ABSTRACT

Excitons, or coupled electron-hole excitations, are important both for fundamental optical properties of materials as well as and for the functionality of materials in opto-electronic devices. Depending on the material they are created in, excitons can come in many forms, from Wannier–Mott excitons in inorganic semiconductors, to molecular Frenkel or bi-molecular charge-transfer excitons in disordered organic or biological heterostructures. This multitude of materials and exciton types poses tremendous challenges for ab initio modeling. Following a brief overview of typical ab initio techniques, we summarize our recent work based on Many-Body Green’s Functions Theory in the GW approximation and Bethe–Salpeter Equation (BSE) as a method applicable to a wide range of material classes from perfect crystals to disordered materials. In particular, we emphasize the current challenges of embedding this GW-BSE method into multi-method, mixed quantum-classical (QM/MM) models for organic materials and illustrate them with examples from organic photovoltaics and fluorescence spectroscopy. Our perspectives on future studies are also presented.

摘要

激子或耦合的电子-空穴激发，对于材料的基本光学性能以及光电设备中材料的功能性都很重要。取决于它们所产生的材料，激子可以有多种形式，从无机半导体中的Wannier-Mott激子到无序有机或生物异质结构中的分子Frenkel或双分子电荷转移激子。大量的材料和激子类型对从头算建模提出了巨大的挑战。在对典型的从头算技术进行简要概述之后，我们基于GW中的Many-Body Green's Functions Theory总结了我们最近的工作近似和Bethe–Salpeter方程（BSE）作为适用于从完美晶体到无序材料的各种材料类别的方法。特别是，我们强调了将GW -BSE方法嵌入有机材料的多方法，混合量子经典（QM / MM）模型中的当前挑战，并以有机光伏和荧光光谱为例进行了说明。还介绍了我们对未来研究的看法。