Electroplated contacts and porous silicon for silicon based solar cells applications

• Uniformity of the Ni–Si interface is crucial for performance of Cu–Ni contacts on Si.
• Uniformly filled PS is the key to obtain the best performance of Cu–Ni contacts on Si.
• Optimization of anodization and electroplating allows complete filling of PS layer.
• Highly adhesive and low contact resistance Cu–Ni contacts are obtained on Si.

In this paper, a two-layer metallization for silicon based solar cells is presented. The metallization consists of thin nickel barrier and thick copper conductive layers, both obtained by electrodeposition technique suitable for phosphorus-doped 70–90 Ω/sq solar cell emitter formed on p-type silicon substrate. To ensure the adhesion between metal contact and emitter a very thin layer of mesoporous silicon is introduced on the emitter surface before metal deposition. This approach allows metal anchoring inside pores and improves silicon–nickel interface uniformity. Optimization of metal contact parameters is achieved varying the anodization and electrodeposition conditions. Characterization of contacts between metal and emitter is carried out by scanning electron microscopy, specific contact resistance and current–voltage measurements. Mechanical strength of nickel–copper contacts is evaluated by the peel test. Adhesion strength of more than 4.5 N/mm and contact resistance of 350 μΩ cm2 on 80 Ω/sq emitter are achieved.