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Impact of laser treatment on phosphoric acid coated multicrystalline silicon PV-wafers

: Geier, M.; Eberstein, M.; Grießmann, H.; Partsch, U.; Völkel, L.; Böhme, R.; Mann, G.; Bonse, J.; Krüger, J.

Postprint urn:nbn:de:0011-n-2038930 (657 KByte PDF)
MD5 Fingerprint: 7b80b807884b6bbf9aaab335e305cadc
Created on: 31.10.2012

European Commission:
26th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC. Proceedings : 5th to 9th September 2011 at the CCH - Congress Centre and International Fair Hamburg in Germany
München: WIP-Renewable Energies, 2011
ISBN: 3-936338-27-2
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <26, 2011, Hamburg>
Conference Paper, Electronic Publication
Fraunhofer IKTS ()

The selective emitter is a well-known technology for producing highly doped areas under the metallization grid to improve the solar cell performance. In this work, the influence of laser irradiation on phosphoric acid coated multicrystalline silicon PV-wafers on the wafer surface structure, the phosphorous depth distribution and the electrical contact resistance within the laser treated area as well as the electrical series resistance of laserprocessed solar cells was evaluated. Different laser processing settings were tested including pulsed and continuous wave (cw) laser sources (515 nm, 532 nm, 1064 nm wavelength). Complementary numerical simulations using the finite element method (FEM) were conducted to explain the impact of the laser parameters on the melting behavior (melt duration and geometry). It was found that the melt duration is a key parameter for a successful laser doping process. Our simulations at a laser wavelengths of 515 nm reveal that low-repetition rate (<500 kHz) laser pulses of 300 ns duration generate a melt duration of ~0.35 µs, whereas upon scanning cw-laser radiation at 532 nm prolongates the melt duration by at least one order of magnitude. Experimentally, the widely used ns-laser pulses did not lead to satisfying laser irradiation results. In contrast, cw-laser radiation and scan velocities of less than 2 m/s led to suitable laser doping featuring low electrical resistances in the laser treated areas.