Figure 1. Spectral energy distribution of the two photon fluxes governing photovoltaic energy conversion on earth.

The sun flux, closely originating from a distance diluted 5800 K blackbody source (dashed black line) filtered by the earth atmosphere (solid black line) determines the short circuit current. The earth environment 300 K blackbody flux governs instead the dark saturation current (Magenta dashed line). Note the very large range of absolute values on the Y-axis.