Wave Optics Simulation of Subwavelength Structures within Solar Cells: Integration of RCWA with GenPro4

To further improve the light management and optical performance of solar cells, research into nano-textured interfaces has led to a need for a fast and accurate wave optics model. Currently, within the PVMD group at the TU Delft an optical solar cell simulation tool, GenPro4, is being developed to allow for the quick optimization and analysis of solar cell designs. However, the implemented wave optics model has limited accuracy and thus an alternative model is sought.In this thesis, we researched several rigorous wave optics simulation methods such as: finite element method, finite difference time domain, transfer matrix method, and rigorous coupled wave analysis. Based on three decision criteria (speed, accuracy, and compatibility) the choice of implementing rigorous coupled wave analysis (RCWA) was made. Besides the standard RCWA formulations, a few improvements were made. S-matrices were used to increasespeed and memory efficiency of the program. Furthermore, calculation of the local E-field allowed for the determination of absorption per material in our cell. Lastly, an angular intensity distribution, known as scatter matrix, was produced as output to allow for the full integration with GenPro4.We validated our new model by comparing results of a nano-textured GICS solar cell with previously conducted finite element method (FEM) simulations. Over a large wavelength range our model showed good agreement with the FEM data. However, slight inaccuracies were observed at longer wavelengths (>1000 nm) as simulation of the metal back reflector became infeasible. Highly absorbing materials, such as metals, potentially required several hundred Fourier modes to be modeled accurately. However, simulations with such a high number of Fourier modes is not feasible as the computer resources (RAM) and computational timeneeded grow exponentially. Furthermore, for very small textures, RCWA converges with the GenPro4 flat model as is expected for sufficiently small textures.Nevertheless, integration of RCWA with GenPro4 was achieved. To demonstrate the ability to quickly and easily simulate real work cell designs, a case study of a perovskite/silicon tandem cell was conducted. In the case study, a combination of 16 interface mythologies was simulated and compared. With the optimal combination showing a potential improvement of 2% over the reference cell.Electrical Engineering | Sustainable Energy Technolog