Title :
Analysis of laser-fired local back surface fields using n/sup +/np/sup +/ cell structures
Author :
Glunz, S.W. ; Grohe, A. ; Hermle, M. ; Schneiderlochner, E. ; Dicker, J. ; Preu, R. ; Mackel, H. ; Macdonald, D. ; Cuevas, A.
Author_Institution :
Fraunhofer ISE, Freiburg, Germany
Abstract :
In order to investigate our new LFC process for the formation of local contacts on a dielectrically passivated rear surface, we have analyzed n/sup +/np/sup +/ structures processed identically to the standard n/sup +/pp/sup +/ cells except for the doping type of the base material. For these devices the p/sup +/-emitter is formed point-like at the rear surface by Al-alloying during the LFC process. The observation of voltages above 600 mV is a clear proof of the creation of a local Al diffusion. Since a pn-junction is much more decisive for a solar cell than a BSF, the n/sup +/np/sup +/ structures were used to understand the physics of the LFC contact and to optimize the laser parameters resulting in efficiencies of 20% for n/sup +/pp/sup +/ LFC cells in a resistivity range between 0.5 /spl Omega/cm and 10 /spl Omega/cm.
Keywords :
aluminium; diffusion; doping profiles; electrical resistivity; elemental semiconductors; laser materials processing; passivation; semiconductor junctions; semiconductor-metal boundaries; silicon; solar cells; surface treatment; 0.5 to 10 ohmcm; Al-alloying; Si-Al; dielectrically passivated rear surface; electrical resistivity; laser fired contacts process; laser parameters; laser-fired local back surface fields; local Al diffusion; n/sup +/np/sup +/ cell structures; p/sup +/ emitter; pn junction; solar cell;
Conference_Titel :
Photovoltaic Energy Conversion, 2003. Proceedings of 3rd World Conference on
Conference_Location :
Osaka, Japan
Print_ISBN :
4-9901816-0-3
