Energy levels in an organic semiconductor are mainly determined by the molecular orbital energies of the constituent molecules. Recent studies, however, have revealed that the energy levels can be altered as much as 1 eV by the molecular orientation in the film or the molecular mixing ratio in the binary film, owing to the intermolecular electrostatic interaction. Because of the long-range nature of Coulomb interaction, theory predicts that the electrostatic energy should depend on the sample shape. In this article, we examine the coverage-dependent energy levels of zinc phthalocyanine and per-fluorinated zinc phthalocyanine in the submonolayer region with ultraviolet photoelectron spectroscopy (UPS) and low-energy inverse photoelectron spectroscopy (LEIPS). Using the procedure we reported previously, we separately evaluated the electronic polarization energy and electrostatic energy as a function of coverage. Unlike the electronic polarization, which contributes only as much as 10 meV, the electrostatic energy contributes as much as 120 meV to the coverage-dependent energy shift. We conclude that the shift in energy levels by changing the coverage is attributed to the sample shape-dependent energy level, owing to the long-range nature of the charge–permanent quadrupole interaction.

中文翻译：

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有机半导体中与样品形状相关的能级

有机半导体的能级主要由组成分子的分子轨道能量决定。然而，最近的研究表明，由于分子间的静电相互作用，薄膜中的分子取向或二元薄膜中的分子混合比可以改变多达 1 eV 的能级。由于库仑相互作用的长程性质，理论预测静电能量应取决于样品形状。在本文中，我们用紫外光电子能谱 (UPS) 和低能逆光电子能谱 (LEIPS) 研究了亚单层区域中酞菁锌和全氟化锌酞菁的覆盖能级。使用我们之前报道的程序，我们分别评估了电子极化能量和静电能量作为覆盖率的函数。与仅贡献多达 10 meV 的电子极化不同，静电能量对依赖于覆盖范围的能量偏移贡献多达 120 meV。我们得出结论，由于电荷 - 永久四极相互作用的长程性质，通过改变覆盖范围来改变能级归因于样品形状相关的能级。