arXiv subjects

B. Engels

Publications and source records attributed to B. Engels.

2 recordsLinked to original sources

arXiv2012

Investigation of exciton transport in crystalline thin-films of the organic semiconductor di-indeno-perylene using photoluminescence analyses

The exciton transport in the prototypical organic semiconductor Di-Indeno-Perylene (DIP) has been investigated by means of photoluminescence (PL) quenching and interpreted by an advanced exciton diffusion model including interference effects, quencher penetration as well as non-perfect exciton quenching. X-ray difraction revealed a correlation between the exciton diffusion length of about 90 nm and the structural coherence length of the DIP layers. Temperature dependent studies in a range of 5 - 300 K indicated an incoherent exciton transport above 80 K at activation energies of 10 - 20 meV related to the thickness dependent gradient of exciton density. Below 80 K a coherent exciton transport can be observed by the reduced phonon-interaction at cryogenic temperatures. This manuscript is a pre-final version.

cond-mat.mtrl-sci↗

arXiv2011

First principles calculations of anisotropic charge carrier mobilities in organic semiconductor crystals

The orientational dependence of charge carrier mobilities in organic semiconductor crystals and the correlation with the crystal structure are investigated by means of quantum chemical first principles calculations combined with a model using hopping rates from Marcus theory. A master equation approach is presented which is numerically more efficient than the Monte Carlo method frequently applied in this context. Furthermore, it is shown that the widely used approach to calculate the mobility via the diffusion constant along with rate equations is not appropriate in many important cases. The calculations are compared with experimental data, showing good qualitative agreement for pentacene and rubrene. In addition, charge transport properties of core-fluorinated perylene bisimides are investigated.

cond-mat.mtrl-sci↗