The evolution of Silicon (Si) solar cell technology, from aluminium-back surface field structure to A1-BSF high-performance interdigitated back contact (IBC) and Tunnel oxide passivated contact (TOPCon) structure, is possible because of advances in surface passivation techniques. A passivation layer can reduce the surface recombination losses by minimizing the surface states density by saturating the dangling bonds and by introducing a surface field.

In silicon solar cells, different schemes are used to passivate the surfaces such as silicon dioxide (SiO2), hydrogenated amorphous silicon nitride (SiNy:H), hydrogenated amorphous silicon, high-low junctions. The thermally grown SiO2 is an excellent surface passivation layer. However, thermal oxidation at high temperature (~1000°C) can cause severe bulk lifetime degradation, especially in multi-crystalline silicon wafers. The thermally grown oxide has limited industrial applicability due to low throughput and high cost. Silicon-Oxide (SiO) process, in contrast, is a fast (< 5 minutes), low-temperature (< 40°C) and low-cost process.