The solar industry is in the midst of a historic technological transition. For years, the market has been dominated by P-type PERC (Passivated Emitter Rear Contact) technology, which brought significant efficiency gains and drove down costs. Now, a new battle for supremacy is underway between two N-type solar cell architectures: TOPCon (Tunnel Oxide Passivated Contact) and HJT (Heterojunction Technology). While both represent a leap forward in performance, their distinct technical and economic profiles position them for different roles in the future of solar energy. By comparing manufacturer datasheets, we can uncover the practical differences that will shape the market for years to come.
TOPCon has established itself as the new industry benchmark. Commercial modules from leading manufacturers now achieve efficiencies in the 23–24.4% range, with some high-volume products exceeding 24%. The technology continues to push boundaries, with laboratory records for TOPCon-based cells already surpassing 26%, and tandem perovskite-on-silicon cells reaching ~33.9% efficiency. HJT technology, while commanding a smaller market share, demonstrates an even higher potential for efficiency. Commercial modules are consistently above 24%, with top-tier manufacturers achieving 25%+ in certified testing. Laboratory prototypes have crossed 26.7%, and in bifacial applications with high-albedo surfaces, HJT can deliver system-level energy yields above its nameplate efficiency.
This is a key area where HJT holds a distinct advantage. Its inherent material properties give it a superior temperature coefficient, typically in the range of -0.21% to -0.25%/°C. This means HJT modules lose less power as temperatures rise. In comparison, TOPCon modules have a temperature coefficient of -0.29% to -0.30%/°C. This approximately 20% improvement in temperature performance translates directly to a higher energy yield in hot climates, making HJT a compelling choice for regions with high ambient temperatures.
Bifaciality refers to the ability of a solar cell to absorb light from both its front and rear sides. While both N-type technologies are highly bifacial, their performance differs. TOPCon modules achieve a respectable bifaciality factor of 80-85%, a notable improvement over PERC. However, HJT technology offers a superior bifaciality factor, with datasheets specifying 90-95%. This is due to its symmetrical cell structure and transparent TCO layers, which maximize light absorption from the rear side.
The most significant factor influencing market dominance is cost. TOPCon's major advantage lies in its manufacturing compatibility. By leveraging existing PERC production lines with modest equipment additions, manufacturers can quickly and affordably transition to TOPCon. This has allowed for a massive and rapid scale-up of production capacity, driving down costs and making TOPCon the more economical choice.
HJT has historically required a much higher capital investment due to its specialized low-temperature manufacturing process and different equipment requirements. While this initial cost premium has slowed its widespread adoption, intense R&D and scaling have significantly narrowed the cost gap between the two technologies, a trend that is expected to continue.
Both technologies are a significant improvement over P-type PERC, since N-type silicon is inherently resistant to boron-oxygen light-induced degradation (LID). Datasheets often cite HJT as having extremely low annual degradation rates of ~0.25% after the first year, ensuring strong long-term performance. However, real-world field studies—particularly in desert conditions—have shown that module durability also depends on encapsulation and materials. In some cases, HJT has shown higher-than-expected degradation due to encapsulant reliability, while TOPCon has demonstrated very low long-term losses (e.g., ~0.14% per year in some field trials).
The data from manufacturer datasheets paints a clear picture: HJT is the technically superior technology, offering higher efficiency, better temperature performance, and superior bifaciality. Its design is a clear path to pushing the boundaries of solar cell performance. However, TOPCon offers a more compelling value proposition for the mainstream market. Its ability to scale rapidly and affordably by leveraging existing manufacturing infrastructure has made it the dominant N-type technology.
For consumers and project developers, the choice boils down to a classic trade-off between performance and cost. For applications where maximizing energy yield per square foot is paramount and a cost premium is justified—such as in rooftop or space-constrained projects—HJT remains a top-tier choice. For the utility-scale market and general deployment where the balance of cost-effectiveness and improved performance is key, TOPCon is the clear winner. The ongoing technological race will continue to benefit the entire industry, pushing both technologies to new heights and making solar power more efficient and accessible than ever before.