Microscopic Insights into Charge Formation and Energetics in n-Doped Organic Semiconductors

Abstract

In the molecular doping of organic semiconductors (OSCs), achieving efficient charge generation and managing the energetic cost for charge release from local molecular charge-transfer complexes (CTCs) to the host matrix is of central importance. Experimentally, tremendous progress has been made in this direction. However, the relation between the OSC film structure on a nanoscopic level including different intermolecular geometrical arrangements and the macroscopic properties of doped OSC films is usually only established quite indirectly. Explicit microscopic insights into the underlying doping mechanisms and resulting electronic structure are still scarce and mostly limited to the study of the individual molecular constituents or isolated bimolecular dopant:host complexes. In the present study, we investigate n-type doping of the frequently investigated OSC materials ZnPC and F8ZnPc and their mixtures which are n-doped with 2-Cyc-DMBI in different dielectric environments. We report significant electronic differences for complexes with nominally the same material composition but different geometrical structures. One specific important finding in this context is that complexes containing two adjacent dopant molecules show much reduced ionization energy values which leads to substantially reduced energy cost for charge release. Furthermore, our results demonstrate that important trends toward macroscopic system behavior can already be obtained with increasing size and varying composition of the relatively small molecular dopant–host complexes considered, including systematic shifts in the Fermi level energies in the doped OSC.

Dynamics-induced charge transfer in semiconducting conjugated polymers

“…The Hirshfeld charge decomposition presented in Fig. 1, which was shown to agree well with other charge decomposition schemes, 39,44 was performed by using Multiwfn software 45 . The charge decomposition results for the AIMD simulations shown in Fig.…”

Dynamics-induced charge transfer in semiconducting conjugated polymers

“…The Hirshfeld charge decomposition presented in Fig. 1, which was shown to agree well with other charge decomposition schemes, 39,47 was performed by using Multiwfn software. 48 The charge decomposition results for the AIMD simulations shown in Fig.…”

Microscopic Study of Molecular Double Doping

“…It should be noted that the BS scheme used in general yields an incorrect spin density due to spin contamination; however, this is not the subject of interest in the present work. The method is discussed in detail elsewhere and was successfully applied in previous studies by us and other researchers. − …”