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Which ray is needed for creating energy in a solar cell?

Updated: Sep 5, 2019

Solar energy cells are made from using finely sliced crystalline silicon ingots (monocrystalline silicon and polycrystalline silicon) or thin-film wafers coated in silicon crystal material. Silicon atom with four valence electrons in its outermost electron shell is a semiconductor material. A semiconductor is a special type of material that conducts electricity under certain conditions.

For a solar energy cell, its ability to release electrons when irradiated by light photons depends on the different amounts of light energy of particular wavelengths that it responds to. When light shines on the photovoltaic (PV) semiconductor material, it will reflect some and absorb some of the incident radiation. Particular light energy frequencies in the electromagnetic spectrum have particular amounts of photon energy and the PV material converts those frequencies of energy into direct current electricity.

The light frequencies in the range with the right energy to knock outer valence electrons are in the visible sunlight part of the electromagnetic spectrum. The whole electromagnetic spectrum, from the lowest frequency (longest wavelength) to the highest frequency (shortest wavelength), includes from radio waves, through infrared radiation, visible light, ultraviolet radiation, X-rays, to gamma rays.

Solar panels convert from 380 to 750 nanometres (part of the ultraviolet, most visible light and about half of the infrared wavelengths) into electrical energy.

When solar radiation within that particular frequency range strike the semiconductor material, some photons knock electrons with from their weaker valence bonds and create an electric current. The wavelengths beyond the ultraviolet & infrared frequencies do not have the right energy to dislodge electrons and so their photon energy becomes absorbed as heat.


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