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Analysis of laser-fired local back surface fields using n+np+ cell structures

: Glunz, S.W.; Grohe, A.; Hermle, M.; Schneiderlöchner, E.; Dicker, J.; Preu, R.; Mäckel, H.; Macdonald, D.; Cuevas, A.

Kurokawa, K. ; Institute of Electrical and Electronics Engineers -IEEE-:
3rd World Conference on Photovoltaic Energy Conversion 2003. Proceedings. Vol.B : Joint conference of 13th PV Science & Engineering Conference, 30th IEEE PV Specialists Conference, 18th European PV Solar Energy Conference ; Osaka International Congress Center "Grand Cube", Osaka, Japan, 11 - 18 May 2003
Osaka, 2003
ISBN: 4-9901816-1-1
World Conference on Photovoltaic Energy Conversion (WCPEC) <3, 2003, Osaka>
PV Science and Engineering Conference <13, 2003, Osaka>
PV Specialists Conference <30, 2003, Osaka>
European PV Solar Energy Conference <18, 2003, Osaka>
Fraunhofer ISE ()

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 Omega cm and 10 Omega cm.