Light micrograph of a polycrystalline silicon solar cell. It produces electricity from sunlight (photovoltaic effect), a clean, renewable and ecological energy. We can see a front electrode (-) or finger (made of silver nanoparticles) in a grid of metallic contacts (wide vertical stripe). The pitch of the grid is a trade-off between the shadow and the series resistance. 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. Digital edition. Field of view size: 0.74 x 1.12 mm (0.029 x 0.044 in)