Maximum short circuit current of a solar cell

The figure above is the AM1.5G standard (from NREL). From this  we can calculate the maximum short circuit current, assuming 100% absorption of incident light and 100% conversion rate from number of photons to number of electrons (holes) collected at the electrodes. This corresponds to 100% external quantum efficiency (EQE) and 100% internal quantum efficiency (IQE). Below is the result of the calculation.

The above figure shows maximum short circuit current as a function of band gap. The assumption here is that all the energy above the band gap is absorbed by the photo cell and all the energy below transmits. As one can see for Eg=1.1 eV (Si), one can get 450 A/m^2, which is pretty close to the realization of Si photocell.

Following is the total power of a solar cell as a function of the band gap. One can see that the maximum is at Eg=1.1 eV. On the other hand, the whole range 0.9-1.3 is good values for the power generation.