Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 69: Poster Session: II-VI semiconductors; Organic semiconductors; Heterostructures

HL 69.12: Poster

Mittwoch, 13. März 2013, 16:00–20:00, Poster A

Simulations of electronic states at grain boundaries in polycrystalline naphthalene — •Marko Mladenović, Nenad Vukmirović, and Igor Stanković — Scientific Computing Laboratory, Institute of Physics Belgrade, University of Belgrade, Serbia

One of the limiting factors for charge carrier transport in polycrystalline organic semiconductors based on small molecules are grain boundaries. We investigated the electronic structure of grain boundaries in polycrystailline organic semiconductor naphthalene. Energy of the system was modeled using TraPEE potential for the interaction between atoms. Atomic structure was obtained by a Monte Carlo method. Electronic structure was obtained using the Charge patching method (CPM) [1], which is based on Density Functional Theory (DFT).

Results for small systems (1000 molecules) indicate that grain boundaries produce trap energy states within the band gap of the material. These states are localized on molecule pairs (called trapping pairs) at the grain boundaries with the distance between molecules significantly smaller than the distance between two adjacent molecules in a naphthalene crystal. Strong correlation between trapping pair mutual distance and trap state energy relative to the top of the valence band energy was found. As a consequence, on the basis of the densities of trapping pairs, densities of trap states for bigger systems (100 000 molecules) were calculated.

[1] N. Vukmirovic, L. Wang, J. Chem. Phys. 128, 121102 (2008)