Spatial Anisotropy of Charge Transfer at Perfluoropentacene–Pentacene (001) Single-Crystal Interfaces and its Relevance for Thin Film Devices

Abstract

Archetypal donor–acceptor (D–A) interfaces composed of perfluoropentacene (PFP) and pentacene (PEN) are examined for charge transfer (CT) state formation and energetics as a function of their respective molecular configuration. To exclude morphological interference, our structural as well as highly sensitive differential reflectance spectroscopy studies were carried out on PFP thin films epitaxially grown on PEN(001) single-crystal facets. Whereas the experimental data supported by complementary theoretical calculations confirm the formation of a strong CT state in the case of a cofacial PFP–PEN stacking, CT formation is energetically less favorable and thus absent for the corresponding head-to-tail configuration as disclosed for the first time. In view of technological implementations, the knowledge gained on the single-crystal references is transferred to thin-film diodes composed of either stacked PFP/PEN bilayers or mixed PFP:PEN heterojunction interfaces. As demonstrated, their electronic and electroluminescent behavior can be consistently described by the absence or presence of interfacial CT states. Thus, our results hint at the thorough design of D–A interfaces to achieve the highest device performances.

Nuclear dynamics of singlet exciton fission in pentacene single crystals

“…S10). From out-of-plane x-ray diffraction measurements, the common pentacene bulk crystal phase, characterized by the (001) lattice distance of 14.1 Å, is identified ( 25 , 26 , 52 ). A comparison of the experimental electron diffraction pattern of the cut crystal platelets with simulated patterns is shown in fig.…”

Orbital-resolved Observation of Singlet Fission

“…The 96 h growth period finishes with an additional 12 h cool-down phase to minimize thermal stress. As analyzed elsewhere 46 , the crystals adopt the low-temperature bulk phase 47,48 and the plate-like habit is dominated by the large (001)-facet which was consequently probed by our trARPES measurements. Thus we can investigate the dynamic population of the excitonic band structure between the photophysically relevant nearest neighbors within the pentacene crystal.…”

Thin films of electron donor–acceptor complexes: characterisation of mixed-crystalline phases and implications for electrical doping

“…in co-deposited films, and absent in head-to-tail configurations. 95,96 Here we report on anisotropy of vibrational features. The complex-related infra-red modes are present only by applying grazing incidence for the light and are absent in infra-red and Raman measurements with normal incidence/detection directions.…”