Oligothiophene-F4TCNQ电荷转移复合物的电子和光学性质：给体共轭长度的作用
Electronic and Optical Properties of Oligothiophene-F4TCNQ Charge-Transfer Complexes: The Role of Donor Conjugation Length
摘要：
从第一性原理多体理论出发，研究了掺杂有机半导体中给体共轭长度对形成部分电荷转移的电荷转移复合物（CTC）的影响。我们考虑了具有4到10个偶数个环的低聚噻吩（nT），其被强受体2，3，5，6-四氟-7，7，8，8-四氰基醌二甲烷（F4 TCNQ）掺杂。随着nT尺寸的增加，电子能隙的减小是由电离能的减小驱动的，而电子亲和力几乎保持恒定。光学带隙表现出不同的趋势，无论施主长度如何，都处于大致相同的能量。第一激发在所有系统中保持相同的振子强度和Frenkel样特征。虽然在4 T-F4 TCNQ中，更高能量的激发也保留了这种性质，但在具有较长nT低聚物的CTC中，位于供体上的电荷转移激发和Frenkel激子出现在吸收开始之上。我们的研究结果提供了重要的洞察CTC的结构-性能关系，从而有助于更深入地了解掺杂的有机半导体。
英文摘要：
We investigate from first-principles many-body theory the role of the donor conjugation length in doped organic semiconductors forming charge-transfer complexes (CTCs) exhibiting partial charge transfer. We consider oligothiophenes (nT) with an even number of rings ranging from four to ten, doped by the strong acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4TCNQ). The decrease of the electronic gaps upon increasing nT size is driven by the reduction of the ionization energy with the electron affinity remaining almost constant. The optical gaps exhibit a different trend, being at approximately the same energy regardless of the donor length. The first excitation retains the same oscillator strength and Frenkel-like character in all systems. While in 4T-F4TCNQ also higher-energy excitations preserve this nature, in CTCs with longer nT oligomers charge-transfer excitations and Frenkel excitons localized on the donor appear above the absorption onset. Our results offer important insight into the structure-property relations of CTCs, thus contributing to a deeper understanding of doped organic semiconductors.
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