Identification of an organic semiconductor superlattice structure of pentacene and perfluoro-pentacene through resonant and non-resonant X-ray scattering

Abstract

Identification of an organic semiconductor superlattice structure of pentacene and perfluoro-pentacene through resonant and non-resonant X-ray scattering Highly crystalline and stable molecular superlattices are grown with the smallest possible stacking period using monolayers (MLs) of the organic semiconductors pentacene (PEN) and perfluoro-pentacene (PFP). Superlattice reflections in X-ray reflectivity and their energy dependence in resonant soft X-ray reflectivity measurements show that PFP and PEN MLs indeed alternate even though the coherent ordering is lost after ∼ 4 ML. The observed lattice spacing of 15.9 Å in the superlattice is larger than in pure PEN and PFP films, presumably because of more upright standing molecules and lack of interdigitation between the incommensurate crystalline PEN and PFP layers. The findings are important for the development of novel organic quantum optoelectronic devices. C

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

“…Dopant density also determines doping efficiency because additional ionized dopants favor charge separation . It must be stressed that the open question of doping efficiency cannot be treated completely apart from those of molecular structures, miscibility, morphology, defects, impurities (notably water and oxygen), and device stability . Charge transport within doped organic semiconductors is thermally activated.…”

“…One can conclude from this short discussion that a plethora of electronic situations occur or even coexist depending on semiconductor‐dopant pairs, temperature, film thickness, and sample preparation conditions . Structural and morphological control upon doping polycrystalline or single crystal thin films of molecular semiconductors is particularly challenging, although not so often considered .…”

“…Superlattice, i.e., a periodic structure of layers of two or more materials, are also highly desirable in the context of doping . Such an unusual arrangement has been observed for blends of pentacene 1 with perfluoropentacene 7 . Doping is generally conducted on polycrystalline thin films, but Masahiro Hiramoto and co‐workers have succeeded to grow single crystals of rubrene 3 doped with minute amounts of FeCl 3 .…”

Optical Absorption Properties in Pentacene/Tetracene Solid Solutions

“…For the structural analysis, we performed XRR measurements, with the results shown in Figure . Acene molecules are known to be oriented close to upright standing for thin films grown at about room temperature on weakly interacting substrates such as native silicon and quartz glass. ,− Therefore, the direction perpendicular to the substrate mainly coincides with the long molecular axis, for which the largest difference in the molecular structures of TET and PEN exists. In an XRR experiment, the out-of-plane lattice spacing is measured with high precision.…”

Computational insights into intriguing vibration-induced pulsing diradical character in perfluoropentacene and the perfluorination effect

“…22,23 Thanks to perfluorination, a successful strategy to functionalize acenes without largely altering their molecular structures, 21,[30][31][32][33][34][35][36][37][38] perfluoropentacene was obtained experimentally and investigated broadly. [32][33][34][35][36][37][38][39][40] In particular, perfluorination can transform pentacene from a p-type semiconductor to an n-type one, assigning perfluoropentacene with higher electron mobility, and thus find a more widespread application prospect in organic electronics. 32,[34][35][36][37] Besides, perfluorination can considerably stabilize the frontier molecular orbitals including the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of pentacene, resulting in an increase of oxidation resistance (Fig.…”