Abstract
This work demonstrates that the application of plated Ni/Cu/Ag contacts for TOPCon solar cells and modules is a reliable alternative to screen-printed metallization. Key advantages of plated metallization is a significant reduction of material costs [B. Grübel et al., in Proceedings 11th SiliconPV Conference, Hamelin, 2021, to be published] due to the substitution of a fully printed silver finger by a stack of a thin nickel seed layer (0.5-1 μm height), highly conductive copper finger (3–10 μm height) and an ultra-thin surface finish by tin (1–3 μm height) or silver (<0.5 μm height). In this study it will be shown that conventional soldering technology can be used to interconnect plated TOPCon solar cells. We manufactured a 60-cell module using industrial processes. The right choice of plating electrolyte allows low stress and ductile metal finger leading to similar reliability in cell breakage experiments compared to state-of-the-art screen-printing metallization.
Highlights
The learning curve of state-of-the-art passivated emitter and rear cells (PERC) [1] is flattening towards cell efficiencies above 24%
This work demonstrates that the application of plated Ni/Cu/Ag contacts for tunnel oxide passivated contact (TOPCon) solar cells and modules is a reliable alternative to screen-printed metallization
This shows that the applied plating process for bifacial TOPCon solar cells did not increase the risk of wafer breakage compared to screen printed TOPCon solar cells or state-of-the-art PERC solar cells
Summary
The learning curve of state-of-the-art passivated emitter and rear cells (PERC) [1] is flattening towards cell efficiencies above 24%. The introduction of solar cell designs with passivated contact such as tunnel oxide passivated contact (TOPCon) solar cells is one possible solution to achieve cell efficiencies of 25% and above [2]. The TOPCon design comes along with the replacement of aluminium based contacts (PERC) with highly conductive metal contacts such as silver or copper on the rear side. Recent publications pointed out that the application of silver based contacts on front and rear side of the solar cell will eventually lead to significant restrictions in silver supply for a growing PV market heading towards a Terawatt scale within the ten years [4,5]. This work demonstrates that this concern can be eliminated by the right choice of plating electrolyte and plating conditions
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