Towards simultaneous double-side Ni/Cu plated contacts on wet etch opened TOPCon solar cells

Ni/Cu metallization of TOPCon as an alternative to screen printed silver has been widely studied with laser contact opening (LCO) and sequential single-sided electroplating on both sides, with good performance results but some thermal-induced damage. Here, an innovative simultaneous double-side electroplating is presented, with wet etch opening of the passivation layers on the TOPCon precursor samples. Etching time longer than expected is needed for both sides, with wettability issues on the front and slower etch rate of the rear SiN<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</inf>. Adhesion is not acceptable for the electrodeposited metallization and the uniformity is poor when residual passivation is present, but despite these challenges a maximum V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</inf> of 682 mV is obtained. Overall, the simultaneous double-side electroplating of Ni/Cu contacts works and wet etching requires further improvements to provide good conditions that can provide both good IV performance and good metallization.