Méndez Henry, Heimel Georg, Winkler Stefanie, Frisch Johannes, Opitz Andreas, Sauer Katrein, Wegner Berthold, Oehzelt Martin, Röthel Christian, Duhm Steffen, Többens Daniel, Koch Norbert, Salzmann Ingo
Humboldt-Universität zu Berlin, Institut für Physik and IRIS Adlershof, AG Supramolekulare Systeme, Brook-Taylor Straße 6, 12489 Berlin, Germany.
Departamento de Física, Pontificia Universidad Javeriana, Carrera 7, No. 43-82 Ed. 52 Of. 606, Bogotá, Colombia.
Nat Commun. 2015 Oct 6;6:8560. doi: 10.1038/ncomms9560.
Ground-state integer charge transfer is commonly regarded as the basic mechanism of molecular electrical doping in both, conjugated polymers and oligomers. Here, we demonstrate that fundamentally different processes can occur in the two types of organic semiconductors instead. Using complementary experimental techniques supported by theory, we contrast a polythiophene, where molecular p-doping leads to integer charge transfer reportedly localized to one quaterthiophene backbone segment, to the quaterthiophene oligomer itself. Despite a comparable relative increase in conductivity, we observe only partial charge transfer for the latter. In contrast to the parent polymer, pronounced intermolecular frontier-orbital hybridization of oligomer and dopant in 1:1 mixed-stack co-crystallites leads to the emergence of empty electronic states within the energy gap of the surrounding quaterthiophene matrix. It is their Fermi-Dirac occupation that yields mobile charge carriers and, therefore, the co-crystallites-rather than individual acceptor molecules-should be regarded as the dopants in such systems.
基态整数电荷转移通常被视为共轭聚合物和低聚物中分子电掺杂的基本机制。在此，我们证明，相反，在这两种类型的有机半导体中可能会发生根本不同的过程。利用理论支持的互补实验技术，我们将一种聚噻吩（据报道分子p型掺杂导致整数电荷转移局限于一个四噻吩主链段）与四噻吩低聚物本身进行了对比。尽管电导率有相当的相对增加，但我们观察到后者只有部分电荷转移。与母体聚合物不同，在1:1混合堆积共晶体中，低聚物和掺杂剂之间明显的分子间前沿轨道杂化导致在周围四噻吩基质的能隙内出现空电子态。正是它们的费米 - 狄拉克占据产生了移动电荷载流子，因此，在这类系统中，共晶体而非单个受体分子应被视为掺杂剂。
