Calculating the generation function of III-V solar cells

Modelling the electrical response of a III-V solar cell requires an exact knowledge of the distribution of photogenerated electron hole pairs G(z) within the solar cell structure. Also, this generation function, connects the optical with the electrical part of a solar cell model. In contrast to silicon solar cells, 99 % of the light is absorbed in the first few microns for a III-V solar cell. Therefore, interference effects have to be taken into account. Four different methods to calculate G(z) of a dual-junction solar cell have been used. The method of characteristic matrices turned out to describe G(z) in a fast and elegant way. Using the calculated G(z), the observed wavy shaped external quantum efficiency (EQE) of the dual-junction (DJ) bottom cell can be explained. In this context, the effects of the top cell thinning method on the EQE are discussed.