Reivindicaciones

1. Intermediate band solar cell characterized for the inclussion of a grid of centres or diffraction lines either on the front or the rear face or even on an internal layer of the cell between two different reffraction index materials, deviating sunlight laterally into the cell, and increasing the light' absorption as the number of transitions also increase (in these kind of cells, transitions occur either between the valence and the intermediate band, between the intermediate and the conduction band, or even simultaneously. 2. Intermediate band solar cell, according to Claim 1, characterised for the centres or difraction lines separating to media of different difraction index are made of: - pyramids of polygonal base. - planes forming a diedro - any of the above repeated according to a periodical pattern. 3. Intermediate band solar cells, according to claims 1 to 2, in which the centres or difraction lines are spaced in a way that for at least one of the directions of illumination and for photons of a given wavelenfth in vacuum, the directions of constructive interference are parallel to the plane in which the solar cell is fabricated. 4. Intermediate band solar cell, according to claims 1 to 3, characterised by including a dielectric Bragg reflector (48) (made up by sucessive layers of low and high reffraction indexes semiconductor) placed, on, under or in the middle of the buffer layer (2) with the aim of refflecting diffracted quasi-horizontal plane waves. 5. Intermediate band solar cell, according to Claim 1 to 3 or 4 characterized by the lower metallic contact (7) is substituted by a side metallic contact taken from the buffer layer (2) in order to easy the acces to the rear face of the cell, so the diffraction structure (9) can be engraved on it and operates at total internal reflection. 6. Intermediate band solar cell according to Claims 1 to 3 or 4 or 5 characterised by the intermediate band materias is formed by a quantum dot matrix or by alloys that incorporate deep centres into the semiconductor.