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Passivation-induced cavity defects in laser-doped selective emitter Si solar cells - formation model and recombination analysis

: Geisler, C.; Kluska, S.; Hopman, S.; Glatthaar, M.


IEEE Journal of Photovoltaics 5 (2015), No.3, pp.792-798
ISSN: 2156-3381
ISSN: 2156-3403
Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit BMUB
0325586B; rEvolution
Journal Article
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien; Dotierung und Diffusion; Oberflächen - Konditionierung; Passivierung; Lichteinfang; Kontaktierung und Strukturierung; Herstellung und Analyse von hocheffizienten Solarzellen; Laser; QSSPC; Emitter; SiNx; ablation

Laser-induced selective Si doping and simultaneous ablation of a dielectric passivation layer is a promising technology for the creation of efficient and cost-effective solar cells. In this paper, the electrical quality of emitters produced with a 532-nm continuous-wave laser will be discussed using elaborate analysis of quasi-steady-state photoconductance (QSSPC) measurements. It will be shown that these emitters cause good charge carrier shielding, which leads to emitter saturation current densities as low as 240 fA/cm2 for unpassivated surfaces. If an SiNx layer is present during laser doping, the emitter recombination increases by a factor of three. This detrimental effect is put down to the formation of microcavities within the recrystallized Si. A model of the ablation mechanism and cavity formation for long laser pulses is proposed, with the experimental data in this study serving as a limiting case for long irradiation lengths.