Light micrograph of a polycrystalline silicon solar cell. It produces electricity from sunlight (photovoltaic effect), a clean, renewable and ecological energy. The front electrodes (-) are shown in a grid of metallic contacts. The bus bar are horizontal and the fingers (made of silver nanoparticles) are wide vertical stripes. 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. Field of view size: 1.49 x 2.23 mm (0.059 x 0.088 in)