The actual electronic band structure of a rubrene single crystal

Abstract

A proper understanding on the charge mobility in organic materials is one of the key factors to realize highly functionalized organic semiconductor devices. So far, however, although a number of studies have proposed the carrier transport mechanism of rubrene single crystal to be band-like, there are disagreements between the results reported in these papers. Here, we show that the actual dispersion widths of the electronic bands formed by the highest occupied molecular orbital are much smaller than those reported in the literature, and that the disagreements originate from the diffraction effect of photoelectron and the vibrations of molecules. The present result indicates that the electronic bands would not be the main channel for hole mobility in case of rubrene single crystal and the necessity to consider a more complex picture like molecular vibrations mediated carrier transport. These findings open an avenue for a thorough insight on how to realize organic semiconductor devices with high carrier mobility.

Photoelectron spectroscopy on single crystals of organic semiconductors: experimental electronic band structure for optoelectronic properties

“…These results means that the valence band of rubrene exhibit a gutter-like shape in the SBZ. This strongly anisotropic character of the valence band was also pointed out by Ding et al and later by Nitta et al, 131,132 whereas their ARUPS results failed to reproduce the valence band structure probably because of insufficiencies in the resolution of the data and/or in cancelation of the sample charging. ‡ ‡ Vollmer and coworkers clearly demonstrated the anisotropic character by a 2-D mapping of the valence band using an angle-resolved time-of-flight (ARTOF) electron energy analyzer.…”

First-principles calculations of hybrid inorganic–organic interfaces: from state-of-the-art to best practice

“…If the initial guess is particularly bad (e.g., when using SAD-densities for systems with very large interface dipoles), it is useful to employ linear mixing for the first few (5)(6)(7)(8)(9)(10) iterations. This allows the SCF to reach a "harmonic" part of the solution space, where the more sophisticated approaches described below can take over.…”

Hot-Carriers’ Effect on the Performance of Organic Schottky Diodes

“…In the following calculation, the indium/rubrene single crystal diode has been chosen for the calculation. The barrier height at the indium/rubrene single-crystal interface is 1.0 eV (µ = 0.85 cm 2 V −1 s −1 , N A = 2.47 × 10 14 cm −3 , and V BI = −0.66 V) [12], the dielectric constant of rubrene is 3 [13], and the effective hole mass in rubrene values from 0.65m 0 to 1.3 m 0 (m 0 is the free electron mass) [18]. 2a clearly shows that a negative electric field in the space-charge will be found when a forward voltage is applied to the diode.…”

“…Organic semiconductor-based devices have been widely studied due to their flexibility, large area, and low-cost processability [1]- [18]. Organic semiconductor diodes are one of the basic building blocks of the modern semiconductor industry and organic semiconductors are still in the developmental phase.…”

“…Therefore, understanding the physics behind the operation of organic semiconductor diodes (the mechanisms governing charge transport and charge recombination) is helpful to improve the performance of organic semiconductor-based devices. A debatable issue occurs because there are different charge transport mechanisms in organic semiconductor-based devices [9]- [18]. A conventional band like description [9] and hopping incoherently from molecule to molecule [10] in organic semiconductorbased devices have been reported.…”