DOUBLE-SIDED N+-P-N+ SOLAR-CELL FOR BIFACIAL CONCENTRATION

The concentration gain that can be achieved with static concentrators is maximum if bifacial cells are used; it is twice the concentration gain of conventional cells. A theoretical and experimental analysis of the properties of an n** plus -p-n** plus transistor-like structure is presented. In this cell the quantum collection efficiency is enhanced by rear junction collection. Series resistance is increased because of the lateral flow of current in the base. A new two-dimensional model for calculating the series resistance and the fill factor is experimentally verified. The model permits the design of optimum metallization grid patterns which reduce the effect of series resistance to acceptable levels. A curve factor of 0. 77 at 5 air mass one suns and 28 degree C was measured in the experimental cells. Potential improvements which could be made are summarized.