English: The Shockley-Queisser limit for the maximum possible efficiency of a solar cell. The x-axis is the bandgap of the solar cell, the y-axis is the highest possible efficiency (ratio of electrical power output to light power input). (Assumes a single-junction solar cell under unconcentrated light, and some other assumptions too.) The curve is wiggly because of IR absorption bands in the atmosphere: I used the actual AM1.5G solar spectrum data. Sometimes people approximate the solar spectrum by a 6000K blackbody spectrum instead, and they get a smoother curve with slightly different values. I cross-checked my curve with an independently-calculated ones and they agree to high accuracy, [1] [2].