UV-stable surface passivation for crystalline silicon cells in solar modules with UV light transmitting encapsulation materials
Robert Witteck1, Philip Jäger1, Martin Rudolph1, Heiko Mehlich2, Marc Köntges1, Thorsten Dullweber1, Rolf Brendel1,3, Henning Schulte-Huxel1, Hans-Peter Sperlich2, Marcel König2, Gunnar Köhler2, Dirk Landgraf2
1Institute for Solar Energy Research Hamelin (ISFH), Emmerthal, Germany
/2Meyer Burger Germany, Hohenstein-Ernstthal, Germany
/3Leibniz University Hannover, Hanover, Germany

This contribution investigates the ultraviolet (UV) stability of die­lectric passivation layers on n+-type industry-typical phosphorus diffused emitters having saturation current densities J0e in the range of 28 fA cm–2 to 75 fA cm–2. We prepare symmetrical silicon wafer test structures with various types of passivation layers and derive their saturation current densities from carrier life time measurements after exposure to various types of UV lamps. Our results reveal that UV illumination of samples with a typical industrial silicon nitride (SiNx) passivation layer increases the surface recombination. The illumination with narrow band lamps with intensity peak at 312 nm for a UV dose of 80 kWh m–2 significantly in­creases the J0e for these samples from 67 fA cm–2 to 287 fA cm–2. In contrast, a passivation layer stack consisting of a thermally grown silicon oxide and SiNx improves the UV stability of the samples. For this passivation layer stack, the J0e increases from a lower initial value of 36 fA cm–2 to only 41 fA cm–2. This finding allows for UV stable PERC cells in solar modules employing UV light transmitting encapsulation materials for an increased annual yield.