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Multijunction Solar Cell Concept The basic principle on which solar cells work is Photovoltaic ie. they convert the photons from the sunlight into usable electricity. However, in this process neither is all the light absorbed nor does all the photons get converted into electricity. High energy blue light photons do not have all of their energy converted into electricity, some is wasted as heat & low energy red light photons are not absorbed at all. Sunlight is made up of a broad spectrum and depending upon these various wavelengths, photons of light also have different energy levels.Hence, to minimize this wastage & to enhance the efficiency of solar cells, scientists came up with the concept of multijunction solar cells.