Light micrograph of a polycrystalline silicon solar cell. It produces electricity from sunlight (photovoltaic effect), a clean, renewable and ecological energy. The upper surface of the photovoltaic cell is an n-type layer, made of silicon semiconductor material. The blue coating layer of the microcrystals is made of silicon nitride for an anti-reflective effect. In this type of polycrystalline cell, the recombination produced in the boundaries of the faulty crystals reduces the photovoltaic efficiency. Field of view size: 297 x 445 繕m (0.012 x 0.018 in)