Advanced Numerical Simulation Tool for Solar Cells - ASA5

Current amorphous and microcrystalline silicon thin-film solar cells use textured substrates for enhancing the light absorption and buffer and graded layers in order to improve the overall performance of the cells. The resulting solar cell structures are very complex, thus, for a detailed understanding and further optimization computer modeling has become an essential tool. In this article a new version of the Advanced Semiconductor Analysis computer program (ASA5) is introduced, which is particularly suitable for the modeling of these complex solar cell structures. The new features of the ASA program include: a new optical model Genpro3 for calculating the absorption profiles in solar cells with rough interfaces, a simulation mode for metal/insulator/semiconductor (MIS) structures, and a model for Charge Deep-Level Transient Spectroscopy (Q-DLTS) [1]. The Genpro3 model takes both coherent (specular) and incoherent (scattered) light propagation into account. The capabilities of the ASA5 program are demonstrated with simulations of a micromorph silicon tandem solar cell and the simulation of the Q-DLTS signal of an amorphous silicon MIS structure. The illuminated J-V characteristics and the external quantum efficiency of an optimized micromorph silicon solar cell approaching 15% efficiency are presented. Using simulations of the Q-DLTS signal a spatial and energy profile of the defect density of states in amorphous silicon is extracted