Impact of the molecular quadrupole moment on ionization energy and electron affinity of organic thin films: Experimental determination of electrostatic potential and electronic polarization energies
Impact of the molecular quadrupole moment on ionization energy and electron affinity of organic thin films: Experimental determination of electrostatic potential and electronic polarization energies
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DOI：
10.1103/physrevb.97.245206
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发表时间：
2018-06
影响因子：
3.7
通讯作者：
K. Yamada;S. Yanagisawa;T. Koganezawa;K. Mase;N. Sato;H. Yoshida
中科院分区：
文献类型：
--
作者：
K. Yamada;S. Yanagisawa;T. Koganezawa;K. Mase;N. Sato;H. Yoshida
有机分子膜的能级对有机半导体的电子性能有着至关重要的影响。最近，静电能的效应被强调为分子取向依赖性和能级连续调节等奇特现象的起源。然而，该机制的讨论主要基于理论工作，并没有得到实验的充分支持。在这项工作中，我们提出了一种仅根据紫外光电子和低能逆光电子能谱获得的实验数据来评估有机薄膜中静电和电子极化能的程序。我们将其应用于具有三种不同分子取向的 $\mathrm{Si}{\mathrm{O}}_{2}$ 基板上 6,13-并五苯醌薄膜的能级。所得静电能与第一性原理计算、电荷多极相互作用静电能等不同层面的理论结果完全一致。目前的工作还强调了电荷永久四极相互作用的重要性，这是非极性分子薄膜中静电能的主导项。
Energy levels of organic molecular films exert paramount influence on the electronic properties of organic semiconductors. Recently the effect of electrostatic energy was highlighted as an origin of such peculiar phenomena as the molecular-orientation dependence and continuous tuning of energy levels. However, the mechanism has been discussed mostly based on theoretical work and has not been adequately supported by experiments. In this work, we propose a procedure to evaluate the electrostatic and electronic polarization energies in organic films solely from the experimental data obtained by ultraviolet photoelectron and low-energy inverse photoelectron spectroscopies. We apply it to the energy levels of thin films of 6,13-pentacenequinone on $\mathrm{Si}{\mathrm{O}}_{2}$ substrates with three different molecular orientations. The obtained electrostatic energies are fully consistent with the theoretical results at different levels such as the first-principles calculations and the electrostatic energy of charge-multipole interactions. The present work also underlines the importance of the charge-permanent quadrupole interaction which is the leading term of the electrostatic energy in the film of nonpolar molecules.