Passivating Poly-Si Tunnel Junctions with Oxide-based Diffusion Barriers for Interconnection in Perovskite/Si Tandem Solar Cells

This work aims for providing a low-resistive passivating polycrystalline Si tunnel junction (poly-Si TJ) for interconnecting the sub cells in Perovskite/Si tandem solar cells. To oppose the diffusion of dopant atoms during high-temperature processing, the incorporation of an additional diffusion blocking interlayer between the n+ and p+ poly-Si region of the tunnel junction is proposed. Several oxide-based interlayers have been investigated and are here discussed with respect to their deposition technique and structural properties. With the help of such interlayers, the design freedom for passivating poly-Si TJs is highly increased. The interlayers enhance the temperature stability of the layer stack and enable contact resistivities sufficiently low for tandem device application after high-temperature treatments at up to 900 or 950 °C. The poly-Si TJ is thereby compatible with the rear contact formation of the mainstream passivated emitter rear cell (PERC) technology.