Indium-Free Recombination Junctions on Tunnel Oxide Passivating Contacts for Fully Textured Perovskite/Silicon Tandem Solar Cells

A transparent conductive oxide (TCO) acting as a recombination layer in perovskite/silicon tandem solar cells for large-scale industrial production relies on low indium consumption and applicability in a scalable process, such as, for example, direct current sputter deposition. Therefore, we investigate aluminum-doped zinc oxide (AZO) and zinc-doped tin oxide (ZTO) in comparison to commonly used indium tin oxide (ITO) as recombination layers between textured ohmic n-TOPCon substrates and hybrid-processed perovskite solar cells. For TCO deposition on TOPCon, sputter-induced damage is observed that can be cured, enabling a high surface passivation quality and efficient carrier transport. Structural, chemical, and optoelectrical properties of AZO, ZTO, and ITO are studied, and their influence on the hole transport layer formation is investigated. In a second step, perovskite single-junction solar cells on ohmic TCO/n-TOPCon substrates are fabricated to investigate the influence of the TCO variation on device performance. Well-working solar cells on ZTO and ITO are built. A similar tandem solar cell performance is demonstrated when comparing ZTO and ITO recombination layers. Thus, ZTO presents a viable In-free recombination layer deposited in an industrially feasible process without efficiency penalty when compared to ITO.