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Low-Ohmic Contacting of Laser-Doped p-Type Silicon Surfaces with Pure Ag Screen-Printed and Fired Contacts

: Lohmüller, E.; Werner, S.; Norouzi, M.H.; Gutscher, S.; Demant, M.; Saint-Cast, P.; Linse, M.; Bitnar, B.; Palinginis, P.; Neuhaus, H.; Wolf, A.


Physica status solidi. A 214 (2017), Nr.12, Art. 1700587, 5 S.
ISSN: 0031-8965
ISSN: 1862-6300
ISSN: 1521-396X
ISSN: 1862-6319
Fraunhofer ISE ()

The state-of-the-art low-ohmic electrical contacting of highly boron-doped silicon surfaces is based on the use of screen-printed and fired silver-aluminum (Ag-Al) contacts. For these contacts, metal crystallites with depths of up to a few microns are observed at the interface. For screen-printed and fired Ag contacts on phosphorus-doped surfaces, the observed crystallite depths are much smaller. In this work, low-ohmic electrical contacting of local laser-doped p-type silicon surfaces with commercial pure Ag screen-printing paste are demonstrated. The doping layer is based on the "pPassDop" approach, which serves as a passivation layer on the rear side of p-type silicon solar cells. The specific contact resistances are measured down to 1 mu ohmb cm2 for p-type doping densities of about 3Ã1019cm-3 at the silicon surface and finger widths of around 55 mu m. Microstructure analysis reveals the formation of numerous small Ag crystallites at the interface with penetration depths o f less than 80nm. A first implementation of the "pPassDop" approach on 6-inch p-type Cz-Si bifacial solar cells using solely Ag contacts on both sides results in a peak front side energy conversion efficiency of 19.1%, measured on a black chuck with contact bars on both sides.