There are many kinds of light, the light we can see includes red, orange, yellow, green, cyan, blue, purple, etc., called visible light, and the light we cannot see, such as infrared and ultraviolet. Different colors of light have different wavelengths. For photovoltaic cells, it is wavelength-selective, and not all light hitting a photovoltaic cell will have a photovoltaic effect. Only those photons with energy greater than the band gap of the material can generate electron-hole pairs in the material when absorbed, while those photons with energy less than the band gap of the material can only heat the material even if they are absorbed. Instead of generating electron-hole pairs. That is, there is a cut-off wavelength (wavelength limit) for the absorption of light by the material.
The spectral characteristics of photovoltaic cells refer to a law of the different responses of photovoltaic cells to various light. It can also be said that photovoltaic cells have different sensitivities to various wavelengths of light. different photoelectric conversion capabilities.
At present, there are many kinds of semiconductor materials that can be used to produce photovoltaic cells. Different materials have different spectral characteristics and different selection ranges of light, so the cut-off wavelengths are also different. Table 1 lists the cut-off wavelengths of several semiconductor materials.
| Material | Cutoff wavelength/m | Total solar energy that can be absorbed by photovoltaic cells /% |
| silicon | 1.1 | 76 |
| Indium Phosphide | 0.97 | 69 |
| Tombstone Gallium | 0.9 | 65 |
| Cadmium | 0.84 | 61 |
| Selenium | 0.81 | 58 |
| Aluminum antimonide | 0.78 | 57 |
| Cadmium selenide | 0.72 | 51 |
| Gallium phosphide | 0.53 | 28 |
| Cadmium sulfide | 0.5 | 24 |
