Solar energy is composed of a range of different wavelengths, and the energy is not evenly distributed over that range. The following graph shows the distribution of solar energy according to wavelength:

The amount of solar energy available in a range of wavelengths is shown by the area under the red curve and between the lowest and highest wavelengths of the range.

As can be seen from the graph, the highest energy level coincides with the approximate center of the visible range (what we see as a yellowish green) - and so most solar panel builders concentrate their efforts on capturing that high-energy visible radiation.

That seems like a reasonable goal until you recognize that the amount of energy in the infrared region (the area under the curve) is substantially greater than the energy in the visible region!

What this means is that an absorber that reflected all of the visible range (which would make it appear white) but absorbed all of the infrared would capture more than twice the energy of one which captures only the visible range.

Obviously, an absorber that captures both visible and infrared radiation would be superior - and this is exactly what the absorber in the DeSoto Solar panels is designed to do.