Key takeaways:
Edge passivation is being adopted in TOPCon manufacturing to reduce efficiency losses caused by cell cutting
Laser-cut edges introduce defects and recombination centers that can impact fill factor and Voc
ALD-deposited Al₂O₃ has emerged as a mainstream passivation approach because of its conformal coverage and strong field-effect passivation
TOPCon continues to evolve not only through improvements in passivation and metallization, but also through innovations in module integration. One such development is edge passivation, which addresses performance losses that occur when cells are cut into smaller pieces. The aim of this approach is to eliminate these undesired losses. For some background, cutting a fully processed cell in half creates defects along the cut corners. These defects act as recombination centers, leading to performance losses. Edge passivation neutralizes these defects and eliminates the losses. In the process, the passivation layers are precisely applied to the cut edges without undesirable effects on the cell surface.
Regarding execution, Baochen Liao, CTO of Leadmicro, presented the details at the TaiyangNews Solar Technology Conference India 2026. At the core of this process lies the interplay between 2 critical steps – wafer cutting and subsequent edge passivation. Although laser-based thermal separation is often referred to as ‘damage-free’, it introduces several forms of edge damage in reality, including localized melting, thermal stress, lattice dislocations, dangling bonds, and debris. The resulting surface is also inherently non-uniform, with micro-scale roughness that contributes to increased recombination. These edge defects are particularly severe near the p-n junction, with edge-related recombination currents amounting to about 19 nA/cm². These losses are primarily reflected as a dip in the fill factor and, to a lesser extent, Voc degradation. This implies that the better the laser parameters are optimized, the better the cut, so the fewer the defects. Thus, the edge passivation schemes and corresponding results also vary from company to company.
Still, a cut is a cut and needs to be repaired. Given the complex and varied nature of defects present at the laser-separated edges, the passivation scheme must also be varied. It relies on a combination of mechanisms, including chemical passivation and field-effect passivation, supplemented by hydrogenation, thermal treatment, and light soaking, according to Liao. Among the available solutions, while amorphous-silicon-based approaches exist, Al₂O₃-based passivation, typically deposited via ALD, has emerged as the mainstream approach. The factor favoring the preference of aluminum oxide is the strong negative fixed charge of the film. As for deposition technology, ALD facilitates excellent film conformality, enabling uniform coverage even on rough and damaged edge surfaces.
Leading equipment makers, including LAPLACE, Leadmicro, and Ideal Energy, among others, offer edge passivation tools. Depending on the baseline process, different tool vendors and manufacturers have announced efficiency gains ranging from 0.1% to 0.2%.
The text is an edited excerpt from TaiyangNews’ latest report on Cell & Module Technologies Trends 2026, which can be downloaded for free here.