Numerical techniques are a powerful tool to speed up the development of effective light management architectures that improve solar cell performance. We mainly use the state-of-the-art time-harmonic finite element solver JCMsuite, which is developed by JCMwave GmbH, a spin-off of the Zuse Institute Berlin (ZIB). The strengths of the finite-element-method (FEM) and the JCMsuite-software are its outstanding accuracy and convergence, which can outperform comparable methods such as FDTD in respective benchmarks .
The Nano-SIPPE group is a founding partner of the Berlin Joint Lab for Optical Simulations for Energy Research (BerOSE) which was founded by HZB, ZIB and the Free University Berlin in 2014. BerOSE forms an ideal environment for the interaction between experts in 3D optical computation and scientists in the synthesis of nanostructured materials for solar electricity generation, energy storage and photonics.
In Nano-SIPPE, we use 3D optical simulations primarily to study nanophotonic light trapping for highly efficient silicon thin-film solar cells and to investigate large area photonic crystals. Further, we contribute with our numerical expertise to the Helmholtz Innovation Lab HySPRINT.
Besides rigorous Maxwell solvers, which are mainly suited for periodic architectures, we are also very experienced in other simulation techniques that can be used for solar devices. Among those are the coherent-incoherent net radiation method for planar layer stacks [2,3], which can be expanded with the scalar scattering theory for non-periodic nanotextures  and ray tracing for large textures.
Numerical and experimental 1 - R spectra for sinusoidally textured layer stacks. The shown data is for 750 nm pitch. Numerical results were calculated with the 0th - and 1st -order corrections . The two corrections differ because not all diffraction orders that are present in glass can propagate into air. Simulation results are shown for two angles of incidence: θin = 0° (thin lines) and θin = 8° (thick lines). Experimental results were obtained with theta θin = 8°.
-  Maes, B. et al. Simulations of high-Q optical nanocavities with a gradual 1D bandgap. Opt. Express 21, 6794–806 (2013).
-  Becker, C. et al. 5x5cm2 silicon photonic crystal slabs on glass and plastic foil exhibiting broadband absorption and high-intensity near-fields. Sci. Rep. 4, 9–13 (2014).
-  K. Jäger, L. Korte, B. Rech and S. Albrecht, "Numerical optical optimization of monolithic planar perovskite-silicon tandem solar cells with regular and inverted device architectures," Opt. Express 25, A473-A482 (OSA, 2017).
-  K. Jäger, M. Fischer, R. A. C. M. M. van Swaaij and M. Zeman, "A scattering model for nano-textured interfaces and its application in opto-electrical simulations of thin-film silicon solar cells," J. Appl. Phys. 111, 083108 (AIP, 2012).
-  K. Jäger, G. Köppel, D. Eisenhauer, D. Chen, M. Hammerschmidt, S. Burger and C. Becker, "Optical simulations of advanced light management for liquid-phase crystallized silicon thin-film solar cells," Proc. SPIE 10356, 103560F (2017)