Ultra high flux concentrator photovoltaics optimization

A characterization study of ultrasmall ultraefficient multijunction concentrator solar cells under realistic illumination conditions is presented, with emphasis on performance sensitivity to light intensity and distribution. Information of this type is essential in the design and optimization of the latest generations of high-flux photovoltaic systems. Cell miniaturization allows increasing the concentration at which efficiency peaks, facilitates passive heat rejection, and permits the use of all-glass optics. However, few device measurements have been published on ultrasmall cells. Extensive measurements, up to ~5000 suns, on the 1.0 mm2 active region within the busbars are reported and analyzed. The standard model which assumes lumped series resistance was insuficient to account for the experimental results. For that reason a new explicit model which relaxes that assumption was developed and its non-trivial predictions were explored. The combinations of the new model with first order heat transfer corrections agreed much better with the experimental results. The practical orientation of this work is evidenced in its improvement suggestions.