Key takeaways:
TOPCon’s core advantage lies in its advanced rear-side passivation structure that minimizes metal-induced recombination losses
Efficiency improvements continue through refinements in passivation layers, deposition methods, and thermal processing steps
LECO technology has played an important role in improving contact formation and supporting TOPCon’s large-scale deployment
TOPCon is the dominant mainstream high-efficiency cell technology today, thanks to its relatively mature architecture, and ongoing refinements through process optimizations are still underway. At the heart of the TOPCon cell structure is a breakthrough in advanced passivation. The structure not only fulfills the conventional requirement of surface passivation, but also addresses a key limitation of earlier cell architectures – metal-induced recombination at the contacts. By introducing a wider bandgap layer between the metal contact and the silicon absorber, the contact is effectively decoupled electronically from the active region, thereby significantly reducing recombination losses. TOPCon takes this clever approach and applies it specifically to the rear side of the cell.
Several leading PV manufacturers have reached new efficiency heights with TOPCon. Of late, companies are using the cell efficiency metric only for internal evaluation and benchmarking, and module efficiency and power are considered the true metrics for evaluation. However, ITRPV and CPIA provide estimates for stabilized cell efficiencies. As shown in the graph, CPIA estimates that the average TOPCon cell efficiency has increased from 25.7% in 2025 to 26% this year, and is expected to improve by a full percentage point over the next 10 years to 27%. A little on the conservative side, ITRPV estimates that efficiency in 2025 was 25.5% and will take only 2 years to improve by 0.5 percentage points to reach 26% in 2027, but another 8 years for the next 0.5% absolute improvement. TaiyangNews’ latest Cell & Module Technology Trends 2026 Report details the ongoing developments that enable these efficiencies.
The essence of the TOPCon process centers on passivation, specifically the rear-surface engineering of an n-type base wafer. This involves applying an optimal passivation scheme that includes a nano-scale tunneling oxide layer topped with a polysilicon layer, which is then doped. For front-surface passivation, TOPCon cells require a layer of aluminum oxide covered by silicon nitride. The rear passivation stack is typically applied using either low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD), with some processes also utilizing physical vapor deposition (PVD). Additionally, the cell technology incorporates thermal processing steps, such as boron diffusion.
While not new, a discussion on the technological progress of TOPCon cannot be complete without mentioning laser-assisted contact optimization. LECO, which stands for Laser Enhanced Contact Optimization, is a proprietary technology originally developed by Cell Energy (CE) and has perhaps contributed most to the wider deployment of TOPCon, placing it on par with HJT in terms of efficiency. We discuss this technology in detail in the TaiyangNews Cell & Module Technology Trends Report 2025; briefly, it employs lasers to form contacts. Here, a bias voltage and strong light injection with high current density diffuse the silver paste into silicon to form an ohmic contact. The process essentially decouples the metal contact recombination and contact resistivity.
The text is an edited excerpt from TaiyangNews’ latest report on Cell & Module Technologies Trends 2026, which can be downloaded for free here.