Electron affinities of small-molecule organic semiconductors: Comparison among cyclic voltammetry, conventional inverse photoelectron spectroscopy, and low-energy inverse photoelectron spectroscopy
Electron affinities of small-molecule organic semiconductors: Comparison among cyclic voltammetry, conventional inverse photoelectron spectroscopy, and low-energy inverse photoelectron spectroscopy
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DOI：
10.1016/j.orgel.2022.106551
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发表时间：
2022-07-01
影响因子：
3.2
通讯作者：
Yoshida, Hiroyuki
中科院分区：
文献类型：
--
作者：
Kubo, Mihiro;Yoshida, Hiroyuki
有机半导体的电子亲和势(A)是代表电子传输水平的能量参数。固体中A的精确值对于有机半导体器件的检测和设计是必不可少的。原则上，可以用反光电子能谱(IPES)测定固体中的A。然而，由于IPES通常仅对IPES专家可用，因此通常使用更容易获得的方法-循环伏安法(CV)根据在溶液中测量的还原电位E-red来估计A。因此，E-RED到A的转换关系在有机半导体的研究中具有重要的现实意义。另一方面，由于样品损坏和低能量分辨率，以前的IPES数据可能会有大约0.3-0.5 eV的误差。2012年，其中一位作者开发了低能反向光电子能谱(LEIPS)，它能够以0.1 eV的精度测定A。在这项工作中，我们建立了基于LEIPS数据的CV数据E(RED)与固态A之间的关系，并提出了关系A=(1.24+/-0.07)x E-RED+(5.06+/-0.15)eV。我们还讨论了由以前的IPES和现在的LEIPS确定的A值在LUMO光谱起始值和真空度方面的可靠性。
The electron affinity (A) of an organic semiconductor is an energy parameter representing the electron transport level. The precise value of A in a solid is indispensable for examining and designing organic semiconductor devices. In principle, A in a solid can be determined by inverse photoelectron spectroscopy (IPES). However, because IPES is normally available only for specialists of IPES, A is often estimated from the reduction potential E-red measured in solution using a more easily available method, cyclic voltammetry (CV). Thus, the conversion relation from E-red into A is practically important in the research of organic semiconductors. On the other hand, previous IPES data may have errors of about 0.3-0.5 eV owing to sample damage and low energy resolution. In 2012, one of the authors developed low-energy inverse photoelectron spectroscopy (LEIPS), which enables the determination of A with the precision of 0.1 eV. In this work, we establish the correlation between CV data E(red )and solid-state A based on LEIPS data and suggest the relation A = (1.24 +/- 0.07) x e E-red + (5.06 +/- 0.15) eV. We also discuss the reliability of the A values determined by the previous IPES and the present LEIPS in terms of the LUMO spectral onset and the vacuum level.