Optical modeling of light trapping in thin film silicon solar cells using the FDTD method

In this paper we present our recent work on modeling the light propagation in silicon thin film solar cells. The aim is to create a realistic view of the light trapping effects and of the resulting optical generation rate. The focus is on real three dimensional systems. Our software Sentaurus TCAD, developed by Synopsys, has the ability to import real topography measurements and to model the light propagation with the Finite-Difference Time-Domain method (FDTD). The first simulation deals with the glass/TCO system. The electric field and intensity distribution (PowerFluxDensity) are shown as simulation output. The transmission and reflection is compared to real measurements. The second simulation focuses on the optical generation rate in the TCO/a-Si:H system. The distribution of the optical generation is correlated to the interface roughness and furthermore the optical generation is shown for different angles of incidence.