Role of Hydrogen on the ITO/Ag Contact Resistance for Low-Temperature Screen-Printing Metallization of Pero/Si Tandems

The upscaling of perovskite/silicon tandem solar cells is an increasingly important topic in research to bridge the gap between laboratory scale performance and industrial application. This requires adapting well-established technologies to enable the processing of upscaled tandem cell manufacturing steps, including the transparent conductive oxide (TCO) front electrode by magnetron sputtering and the metal contact by screen printing. For state-of-the-art silicon heterojunction (SHJ) solar cells, both the TCO and the metal contact are annealed at temperatures around 200 °C. Perovskite films in contrast are known to degrade at such high temperatures, which makes the processing of the front contact for perovskite based solar cells more challenging. In this work, we demonstrate an optimized screen-printing process that, with the right choice of sputtering process parameters, enables a low TCO/Ag contact resistivity of around 1 mΩcm2at a maximum processing temperature of 135 °C and therefore suitable for (most) perovskite absorbers. The interaction between the TCO and the silver paste is analyzed in detail with respect to achieving low contact resistivity between the two layers. Our results demonstrate that controlling the hydrogen content during the sputtering process is critical: higher hydrogen levels result in a clear increase in the specific contact resistivity. Finally, we show a screen-printed tandem device that further confirms the process feasibility.