Electrical Properties of Intermediate Band (IB) Silicon Solar Cells Obtained by Titanium Ion Implantation

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Castán, Helena
Pérez, Eduardo
Dueñas, Salvador
Bailón, Luis
García Hemme, Eric
Irigoyen Irigoyen, Maite
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American Institute of Physics (AIP)
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Intermediate band silicon solar cells have been fabricated by Titanium ion implantation and laser annealing. A two-layer heterogeneous system, formed by the implanted layer and by the unimplanted substrate is obtained. In this work we present electrical characterization results which evidence the formation of the intermediate band on silicon when ion implantation dose is beyond the Mott limit. Clear differences have been observed between samples implanted with doses under or over the Mott limit. Samples implanted under the Mott limit have capacitance values much lower than the non-implanted ones as corresponds to a highly doped semiconductor Schottky junction. However, when the Mott limit is surpassed the samples have much higher capacitance, revealing that the intermediate band is formed. The capacitance increase is due to the big amount of charge trapped at the intermediate band, even at low temperatures. Titanium deep levels have been measured by Admittance Spectroscopy. These deep levels are located at energies which vary from 0.20 to 0.28 eV bellow the conduction band for implantation doses in the range 10^13-10^14 at/cm^2. For doses over the Mott limit the implanted atoms become non recombinant. Admittance measurements are the first experimental demonstration the Intermediate Band is formation. Capacitance voltage transient technique measurements prove that the fabricated devices consist of two-layers, in which the implanted layer and the substrate behave as an n^+/n junction.
© 2012 American Institute of Physics. International Conference on Ion Implantation Technology (19ª. 2012. Valladolid). This work was partially supported by VA128A11-2 funded by the Junta de Castilla y León, Spanish TEC2011 under grant 27292-C02-01, S/2009/ENE- 1477) funded by the Comunidad de Madrid and CSD2006-00004 funded by the Spanish Consolider National Program. Research of E. Perez was supported by a University of Valladolid FPI grant and research of E. Garcia-Hemme by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM).
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