For example, front surface passivation affects carriers generated near the surface, and since blue light is absorbed very close to the surface, high front surface recombination will affect the "blue" portion of the quantum efficiency. The same mechanisms which affect the collection probability also affect the quantum efficiency. While quantum efficiency ideally has the square shape shown above, the quantum efficiency for most solar cells is reduced due to recombination effects. Quantum efficiency is usually not measured much below 350 nm as the power from the AM1.5 contained in such low wavelengths is low. The quantum efficiency of a silicon solar cell. A quantum efficiency curve for an ideal solar cell is shown below. The quantum efficiency for photons with energy below the band gap is zero. If all photons of a certain wavelength are absorbed and the resulting minority carriers are collected, then the quantum efficiency at that particular wavelength is unity. The quantum efficiency may be given either as a function of wavelength or as energy. The "quantum efficiency" (Q.E.) is the ratio of the number of carriers collected by the solar cell to the number of photons of a given energy incident on the solar cell.
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