Achieving High Efficiencies for Silicon Heterojunction Solar Cells Using Silver-Free Metallization

Abstract

This work investigates the influence of the metallization of low-temperature Cu paste and AgCu paste on the performance of SHJ solar cells through a comprehensive study of two techniques—screen printing (SP) and dispensing. The research successfully applied Cu and AgCu pastes as metal contacts on SHJ solar cells, yielding promising results. Notably, cells with AgCu paste SP on the front side and Ag paste SP on the rear side achieved a 0.13% efficiency gain over reference Ag SP bifacial cells. Moreover, cells with AgCu paste SP on the front side and Cu paste SP on the rear side reached an efficiency of 23.6%, just 0.35% lower than the reference cells, while saving approximately 70% of Ag paste. Cells with Cu paste SP on both sides recorded an average efficiency of 22.4% and a maximum of 23.08%, the highest efficiency reported for cells using Cu SP on both sides (zero Ag). Cells with Cu dispensing on the rear side also demonstrated superior performance compared to cells with Cu SP on the rear side. Along, we assessed the finger-printed characteristics of the three pastes and the performance of SHJ solar cells under various annealing conditions including the Cu annealing conditions (300°C for 5 s). The solar cells maintained stable performance up to 280°C for 5 s, with degradation observed above this temperature, and light soaking partially recovered some of the efficiency loss. A 0.2% drop persisted under Cu annealing conditions, but light soaking reversed this effect back to the original efficiency. This work advances SHJ solar cell technology by highlighting the potential of AgCu and Cu pastes to efficiently replace or reduce Ag paste consumption in SHJ solar cell metallization.