Effects of manufacturing tolerances on micro-CPV module performance

With miniaturization of component sizes in micro-CPV, the accuracy requirements for manufacturing processes increase. We investigate a micro-CPV module based on silicone-on-glass primary optics, spherical ball lenses as secondary optics and 5-junction micro solar cells. In this work, the influence of component dimensions and their alignment on the micro-CPV module performance are investigated using ray tracing modeling as well as experimental measurements. The influence of deviations from ideal such as the lateral position of the spherical lens or the module tilt, on the module performance is analyzed based on modeled flux profiles, optical efficiency, and photo current. Simulations show that the individual tolerances regarding each component are uncritical, related losses remain well below 2% within the considered manufacturing tolerances. However, in real applications combined deviations from ideal are likely to occur, which in general have anisotropic behavior, and complicate the situation. In this work, different deviations related to the spherical ball lens are investigated in detail. Finally, a micro-CPV mono module prototype, was tested outdoors and demonstrated a promising efficiency of 35.6% under prevailing conditions in Freiburg, Germany.