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Descripción
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| More efficient photovoltaic conversion of solar energy has been proposed to be possible by using intermediate band (IB) materials. In these an isolated, partially filled IB within the gap of a semiconductor allows an electron to be excited in the latter from its valence band (VB) to its conduction band (CB) not only by absorption of one photon with energy higher than that of the main gap Eg, but also in two steps, using two photons of lower energy: one photon excites the electron from the VB to the IB, and the other does the same from the IB to the CB. This allows increasing photocurrent without sacrificing output voltage, so that the ideal efficiency limit can be pushed from 40.7 % (the Queisser value) to over 63.2 % (for an optimum Eg value of ¿ 2 eV). In the last years we have indicated, on the basis of DFT simulations, that such IB characteristics can be obtained with typical semiconductors in which an electropositive element is substituted by a judiciously chosen light transition metal and can provide partially filled d electronic states at an appropriate energy position within the bandgap. After having showed with DFT calculations that this is the case with Ga(P,As) or chalcopyrite CuGaS2 in which Ga is substituted by Ti or Cr, we are proposing more recently on a similar basis other semiconductors, suitable for preparation in thin film form, that contain the electropositive element to be substituted (e.g. In, Sn, Sc) in octahedral coordination. Since the latter is the most suitable one for transition metals, the achievement of a high substitution degree needed for good light absorption and for the development of the delocalized characteristics in the IB that can minimize recombination, would be facilitated. Calculations show also that some Sibased structures including transition metal atoms can have IB properties; these allow to explain, in fact, the unusual electric behaviour experimentally observed recently on Tiimplanted Si wafers. For some of the mentioned polar compounds we have carried out the inlab experimental preparation and the verification that sub-bandgap photon absorption takes place, in agreement with the predictions of electronic structure and absorption coefficient provided by quantum modelling. The current status of these different proposals and the last results obtained on these systems will be presented. | |
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Internacional
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Si |
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Nombre congreso
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European Energy Conference |
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Tipo de participación
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960 |
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Lugar del congreso
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Barcelona (España) |
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Revisores
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Si |
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ISBN o ISSN
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00-0000-000-0 |
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DOI
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Fecha inicio congreso
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20/04/2010 |
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Fecha fin congreso
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26/04/2010 |
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Desde la página
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1 |
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Hasta la página
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1 |
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Título de las actas
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Proc. European Energy Conference |