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Koprucki T.,Weierstrass Institute WIAS | Gartner K.,Weierstrass Institute WIAS
Optical and Quantum Electronics | Year: 2013

Inspired by organic semiconductor models based on hopping transport introducing Gauss-Fermi integrals a nonlinear generalization of the classical Scharfetter-Gummel scheme is derived for the distribution function F γ(η) = 1/(\exp (-η)+γ). This function provides an approximation of the Fermi-Dirac integrals of different order and restricted argument ranges. The scheme requires the solution of a nonlinear equation per edge and continuity equation to calculate the edge currents. In the current formula the density-dependent diffusion enhancement factor, resulting from the generalized Einstein relation, shows up as a weighting factor. Additionally the current modifies the argument of the Bernoulli functions. © 2013 Springer Science+Business Media New York.

Koprucki T.,Weierstrass Institute WIAS | Gartner K.,Weierstrass Institute WIAS
13th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2013 | Year: 2013

For Blakemore-type distribution functions F(η) = 1/(exp(-η) +γ) describing the carrier density in semiconductors a generalization of the classical Scharfetter-Gummel scheme can be derived resulting in a nonlinear equation per edge to calculate the edge current. This approach provides a good approximation of the carrier density in degenerate semiconductors for values of the chemical potential η < 1.3kBT. We discuss an extension of this approach based on a piecewise approximation of the distribution function by functions of that type in order improve the approximation for larger values of the chemical potential. © 2013 IEEE.

Koprucki T.,Weierstrass Institute WIAS | Tabelow K.,Weierstrass Institute WIAS
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Mathematical modeling and simulation (MMS) has now been established as an essential part of the scientific work in many disciplines and application areas. It is common to categorize the involved numerical data and to some extend the corresponding scientific software as research data. Both have their origin in mathematical models. In this contribution we propose a holistic approach to research data in MMS by including the mathematical models and discuss the initial requirements for a conceptual data model for this field. © Springer International Publishing Switzerland 2016.

Fischer A.,TU Dresden | Koprucki T.,Weierstrass Institute WIAS | Glitzky A.,Weierstrass Institute WIAS | Liero M.,Weierstrass Institute WIAS | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Large area OLEDs show pronounced Joule self-heating at high brightness. This heating induces brightness inhomogeneities, drastically increasing beyond a certain current level. We discuss this behavior considering 'S'-shaped negative differential resistance upon self-heating, even allowing for 'switched-back' regions where the luminance finally decreases (Fischer et al., Adv. Funct. Mater. 2014, 24, 3367). By using a multi-physics simulation the device characteristics can be modeled, resulting in a comprehensive understanding of the problem. Here, we present results for an OLED lighting panel considered for commercial application. It turns out that the strong electrothermal feedback in OLEDs prevents high luminance combined with a high degree of homogeneity unless new optimization strategies are considered. © 2015 SPIE.

Peschka D.,Weierstrass Institute WIAS | Thomas M.,Weierstrass Institute WIAS | Glitzky A.,Weierstrass Institute WIAS | Nurnberg R.,Weierstrass Institute WIAS | And 5 more authors.
Optical and Quantum Electronics | Year: 2016

We consider a device concept for edge-emitting lasers based on strained germanium microstrips. The device features an inhomogeneous tensile strain distribution generated by a SiN stressor deposited on top of the Ge microstrip. This geometry requires a lateral contact scheme and hence a full two-dimensional description. The two-dimensional simulations of the carrier transport and of the optical field, carried out in a cross section of the device orthogonal to the optical cavity, use microscopic calculations of the strained Ge material gain as an input. In this paper we study laser performance and robustness against Shockley–Read–Hall lifetime variations and device sensitivity to different strain distributions. © 2016, Springer Science+Business Media New York.

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