Photovoltaic devices, which operate by directly converting solar energy into electricity, have become rapidly one of the most important “clean” energy sources. The optimization of thin-film solar cells for such use has been mainly a trial-and-error process. A detailed understanding of the relationships between growth processes, structural defects, strain, and electrical properties would benefit the development of these devices considerably. In the Virtual Institute "Microstructure control for thin-film solar cells", the formation of structural defects and related strain during the growth of thin film solar cells is investigated by combining various experimental as well as simulation approaches.

The goal of this subproject is to derive vector-valued phase field models describing CISe (CIGSe) systems (Wagner, TU Berlin) together with fast, robust, and reliable numerical solution techniques (Kornhuber, FU Berlin). Suitable free energies will be determined by density functional theory (Albe, TU Darmstadt).

Cooperation:

• Prof. Dr. Carsten Gräser
• Prof. Dr. Barbara Wagner (TU Berlin/WIAS)
• Sibylle Bergmann (TU Berlin)
• Prof. Dr. Karsten Albe (TU Darmstadt)
• Dr.-Ing Daniel Amkreutz (Helmholtz-Zentrum Berlin)
• S. Kühnapfel (Helmholtz Zentrum Berlin)
• Priv.-Doz. Dr. Daniel Abou-Ras (Helmholtz-Zentrum Berlin)
• Dr. Roland Mainz (Helmholtz-Zentrum Berlin)

Publications:

Gräser, C. and Kahnt, M. and Kornhuber, R. (2016) Numerical approximation of multi-phase Penrose-Fife systems. Computational Methods in Applied Mathematics, 16 (4). pp. 523-542. ISSN Online: 1609-9389, Print: 1609-4840

Talks:

05/13/2014: R. Kornhuber, Numerical Solution of Multicomponent Phase Field Models, Tagung: Schnelle Löser für Partielle Differentialgleichungen, Mathematisches Forschungsinstitut Oberwolfach

11/03/2014: M. Kahnt, Non-smooth Schur-Newton method for a multi-phase field model of the liquid phase crystallization process, VI Autumn School, Potsdam

09/17/2015: M. Kahnt, Numerical approximations of multi-phase Penrose-Fife systems, European Conference on Numerical Mathematics and Advanced Applications, Ankara, Turkey

11/19/2015: R. Kornhuber, Numerical Approximation of Penrose-Fife systems, Variational Inequality Day, HU Berlin, Berlin

06/16/2016: M. Kahnt, Numerical approximations of multi-component multi-phase systems, 19th European Conference on Mathematics for Industry, Santiago de Compostela, Spain

02/13/2017: M. Kahnt, Phase-field modeling of Si thin-film growth via liquid-phase crystallization, VI Winter workshop on microstructure characterization and modeling for solar cells, Spitzingsee, Germany