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The Shockley–Queisser limit, zoomed in near the region of peak efficiency. In a traditional solid-state semiconductor such as silicon, a solar cell is made from two doped crystals, one an n-type semiconductor, which has extra free electrons, and the other a p-type semiconductor, which is lacking free electrons, referred to as "holes."
The Shockley-Queisser limit for the efficiency of a single-junction solar cell under unconcentrated sunlight. This calculated curve uses actual solar spectrum data, and therefore the curve is wiggly from IR absorption bands in the atmosphere. This efficiency limit of about 34% can be exceeded by multijunction solar cells.
The Shockley–Queisser limit for the efficiency of a single-junction solar cell under unconcentrated sunlight at 273 K. This calculated curve uses actual solar spectrum data, and therefore the curve is wiggly from IR absorption bands in the atmosphere. This efficiency limit of ~34% can be exceeded by multijunction solar cells.
The Shockley-Queisser limit for the theoretical maximum efficiency of a solar cell. Semiconductors with band gap between 1 and 1.5eV (827 nm to 1240 nm; near-infrared) have the greatest potential to form an efficient single-junction cell. (The efficiency "limit" shown here can be exceeded by multijunction solar cells
The numbers are normally not similar as you suggest. But in any case, f c cannot be more than 1, and the upper limit (the Shockley-Queisser limit) requires taking f c = 1. Eric Kvaalen 19:05, 6 September 2016 (UTC) Yes, virtually all above-gap photons come from recombination, but not all recombinations create above-bandgap photons.
Breakdown of the causes for the Shockley-Queisser limit. The black height is Shockley-Queisser limit for the maximum energy that can be extracted as useful electrical power in a conventional solar cell. However, a multiple-exciton-generation solar cell can also use some of the energy in the green area (and to a lesser extent the blue area ...
For a two layer cell, one layer should be tuned to 1.64 eV and the other at 0.94 eV, with a theoretical performance of 44%. A three-layer cell should be tuned to 1.83, 1.16 and 0.71 eV, with an efficiency of 48%. A theoretical "infinity-layer" cell would have a theoretical efficiency of 68.2% for diffuse light. [11]
However, the solar frequency spectrum approximates a black body spectrum at about 5,800 K, [1] and as such, much of the solar radiation reaching the Earth is composed of photons with energies greater than the band gap of silicon (1.12eV), which is near to the ideal value for a terrestrial solar cell (1.4eV).