ZEMAX optical simulation of the illuminance of a 0.25 mm² solar cell as a function of wavelength A) 500 nm (top cell), B) 800 nm (middle cell) and C) 1300nm (bottom cell). The scale on the right of the images corresponds to the effective concentration. The average concentration is 350×, so from the maximum effective concentration of each sub-cell, we can calculate the PAR for each sub-cell: top cell: 2.38, middle cell: 6.85, bottom cell: 15.6.