TU Eindhoven and LONGi Advance ALD ZnO Passivating Contacts, Achieving 24.3 Percent Efficiency in Silicon Solar Cells

Atomic layer deposition of ZnO for contact passivation in silicon solar cells has emerged as a promising alternative to TOPCon technology, with the recent breakthrough of zinc oxide passivating contacts achieving 24.3 percent efficiency in a LONGi solar cell. This development builds on research led by Bart Macco’s group at Eindhoven University of Technology, which pioneered the concept of ZnO passivating contacts. The breakthrough was further demonstrated by LONGi, which successfully integrated the technology into high-efficiency solar cells.

Key advancements include the use of an interfacial SiO2 layer for passivation, Al2O3 capping to retain hydrogen during annealing, and selective Al2O3 removal to enable electrical contact while preserving passivation. The integration of a low-work-function LiF layer has improved contact resistivity, reducing the need for heavy silicon doping.

ALD ZnO offers lower-temperature processing, thinner layers around five nanometers, and elimination of toxic dopants compared to doped poly-Si in TOPCon. With potential advantages in scalability, industrial feasibility, and initial efficiency gains, ZOPCon could surpass TOPCon, though further research is needed to enable bifacial designs, optimize lateral conductivity, and enhance stability for large-scale production.

Sources

Passivating Contacts for Silicon Solar Cells: A Zinc Oxide Breakthrough? – Atomic Limits