Technical boundaries of micro-CPV module components: How small is enough?

With miniaturization of dimensions, new manufacturing methods e.g. from microelectronics may lead to cost reduction of CPV. In this work, we focus on the thermal, electrical and optical boundaries of the micro-CPV module technology with respect to cell and lens miniaturization. Open-circuit voltage losses due to recombination at the solar cell perimeter and dark area as well as high operating temperature are investigated. The smaller the cell the higher the losses due to increased perimeter-to-area ratio. On the other hand, lower optical power per cell leads to lower temperatures and thus increased voltage. Based on the electrical and thermal simulations, an optical configuration for a two-stage optics with plano-convex primary optics and a glass sphere as secondary optical element is presented. Besides optical efficiency, also acceptance angle and flux distribution are considered. Simplified simulations where only two wavelengths are considered compare well with detailed full spectrum simulations. We identify two regions of high optical efficiency. Detailed simulations showed that only in one of the regions, the flux distribution on the solar cell is acceptable. The results are the basis for a module configuration that will be realized as a prototype in future work.