偏振吸收和戴维多夫分裂的本体和薄膜并五苯多晶型,Physical Chemistry Chemical Physics

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偏振吸收和戴维多夫分裂的本体和薄膜并五苯多晶型
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2018-11-14 00:00:00 , DOI: 10.1039/c8cp06384b
Caterina Cocchi _{1,

2,

3,

4} , Tobias Breuer _{4,

5,

6} , Gregor Witte _{4,

5,

6} , Claudia Draxl _{1,

2,

3,

4}

Affiliation

并五苯是研究最多的有机材料之一，尤其是在过去的二十年中，其光学性能一直是研究的重点。尽管有如此广泛的兴趣和迄今获得的广泛知识，但仍在辩论许多问题。最相关的问题之一是多态性的作用及其如何影响最低能量的激子，该激子出现在可见光区域，并受到相当大的达维多夫分裂的影响。我们在理论和实验相结合的工作中解决了这个问题，其中在可见光的整个能量范围内研究了三种并五苯多晶型物的光吸收特性。在多体微扰理论的框架内，从第一原理计算出的光谱直接与偏振分辨吸收率进行了比较，可以测量三种不同的并五苯相（两种本体多晶型物和薄膜相）。通过这种方式，我们可以明确地确定第一个激子的两个达维多夫分量和每个考虑相的光学指纹。在理论和实验之间取得很好的一致性的情况下，我们表明，所有多晶型物在吸收开始时都表现出共同的特征，而与相位有关的特征仅出现在2 eV以上。我们讨论了最低价的单重态和三重态激子的特性，包括深色激子，突出了电子带的贡献以及电子-空穴相互作用和局部场效应的作用。我们明确地确定了第一个激子的两个达维多夫分量和每个考虑相的光学指纹。在理论和实验之间取得很好的一致性的情况下，我们表明，所有多晶型物在吸收开始时都表现出共同的特征，而与相位有关的特征仅出现在2 eV以上。我们讨论了最低价的单重态和三重态激子的特性，包括深色激子，突出了电子带的贡献以及电子-空穴相互作用和局部场效应的作用。我们明确地确定了第一个激子的两个达维多夫分量和每个考虑相的光学指纹。在理论和实验之间取得很好的一致性的情况下，我们表明，所有多晶型物在吸收开始时都表现出共同的特征，而与相位有关的特征仅出现在2 eV以上。我们讨论了最低价的单重态和三重态激子的特性，包括深色激子，突出了电子带的贡献以及电子-空穴相互作用和局部场效应的作用。

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Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs

Pentacene is one of the most studied organic materials and in particular its optical properties have been the subject of intense research during the last two decades. In spite of such a widespread interest and of the extensive knowledge achieved so far, a number of issues are still debated. One of the most relevant questions concerns the role of polymorphism and how it affects the lowest-energy exciton, which appears in the visible region and is subject to a sizable Davydov splitting. We address this problem in a combined theoretical and experimental work, where the optical absorption properties of three pentacene polymorphs are investigated within the whole energy range of visible light. Optical spectra computed from first principles in the framework of many-body perturbation theory are directly compared with the polarization-resolved absorbance, measured for three different pentacene phases (the two bulk polymorphs and the thin-film phase). In this way, we unambiguously identify the two Davydov components of the first exciton and the optical fingerprints of each considered phase. With very good agreement between theory and experiment, we show that all polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, including dark ones, highlighting the contributions from the electronic bands and the role of the electron–hole interaction and of the local-field effects.

更新日期：2018-11-14

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