Abstract: Procedure to obtain semiconductor materials with electronic levels close to the mid-bandgap (deep levels) which do not suffer from the non-radiative recombination by multiple phonon emission (MPE) associated to the existence of that kind of levels. The procedure consist in doping by any means the semiconductor with a density sufficiently high of the impurities producing the deep level, so that a Mott transition of the electron wavefunctions representing the localized states in the impurities is induced, in such a way that these wavefunctions become distributed across the whole semiconductor and are shared by all the impurities. When this happens, local charge density variations, and thus non-radiative recombination by MPE, disappear. Based on the resulting materials (semiconductors with three separate energy bands and radiative behavior (1), (2) and (3)) different optoelectronic devices can be fabricated (solar cells, photodetectors, lasers, etc.

Abstract: The invention relates to a solar cell containing a semiconductor (1) with an intermediate band (2) that is half filled with electrons, located between two layers of ordinary n type (3) and p type (4) semiconductors. When lighted, electron-hole pairs are formed either by a photon that absorbs the necessary energy (5) or by two photons (6,7) that absorb less energy which pump an electron from the valence band to the intermediate band (8) and from the latter to the conductance band (9). An electrical current is generated that exits on the p side and returns via the n side. The n and p layers also prevent the intermediate band from contacting the outer metal connections, which would have resulted in a short-circuit. Said cell converts solar energy into electricity in a more efficient manner than conventional cells and contributes to improvement of the photovoltaic devices.