TOPCon Technology (Tunnel Oxide Passivated Contact) was brought first into the solar industry in 2013 by the German Researchers of Fraunhofer Institute of Solar Energy Systems as the best combination of efficiency and durability about capital cost.

Unlike conventional solar cells, TOPCon Technology aims to improve the efficiency of solar cells by addressing the problem of Conventional cells which utilize metal contacts may often reduce efficiency by blocking some of the incoming light. This new technology uses a thin layer of tunnel oxide deposition between the metal contact and the solar cell creating a tunneling junction for better electron transport and collection. It is the passivation of the cell surface with a thin layer of silicon oxide, the rate of electron recombination is also reduced. Hence, solar panels made from this technology also function better in low-light conditions making them ideal for use in places with less sunlight.

The oxide layer protects the cell from extreme moisture and temperature fluctuations which usually cause gradual degeneration. As a result, this technology ensures higher durability as they are less susceptible to degradation over time.

The Difference between P-Type PERC and N-Type TOPCon
When it comes to cost-effectiveness, PERC Technology is a compromise in efficiency. Although PERC technology is cost-effective and results in better efficiency, the pace of performance improvement through continuous processes in PERC technology is slow.Currently, mainstream P-Type modules have an efficiency of 21.4% which will increase to 22.75% in the next one decade.

Looking identical to a PERC cell, N-Type TOPCon solar cell installed in a in a PV module, both are made from a silicon wafer. However, the difference between the two lies in the way of doing in wafers, which ultimately improves the efficiency and performance.

P-Type wafers are doped with boron, while the N-Type ones are covered with phosphorous which degrades less than boron over time when exposed to oxygen. Moreover, the latter adds free electrons to the wafer which in turn results in increased efficiency.

Today, N-Type modules have an efficiency of close to 22.5% which will eventually enhance to 24% in the next ten years as per estimates.

Nonetheless, the manufacturing process of N-Type module is still expensive.

Advantages of N-Type TOPCon Technology

  1. Manufacturing Process: TOPCon module manufacturing do not require high capital investment for manufacturers as they can be manufactured by the same machinery as P-Type modules.
  2. Higher Efficiency: The efficiency of N-Type Cell PV Modules can go more than 25% unlike PERC Cell has a maximum theoretical efficiency of around 24%.
  3. Lower Degradation: Compared to PERC PV panels TOPCon panels have lower degradation during the 1st year and the 30 years of panel use.
  4. Bifaciality Rate: For TOPCon Panels, the bifacial factor has been determined to be at an average of about 85% compared to PERC PV modules which is at an average of around 70%. The former panels collect more energy from the rear side which is favorable for ground mount utility projects. Moreover, they are aesthetically more appealing than PERC modules as they are made to achieve a distinctive dark appearance- full black solar panels which are put through various design and manufacturing techniques that minimize visible reflections and bright colours.
  5. Low-Light Performance: TOPCon modules function more efficiently in low-light conditions while extending the electricity generation period during the day and hence improving the performance of the installation over time.

Challenges of TOPCon Technology:

While TOPCon is far more superior in terms of reliability and efficiency compared to PERC cells, the former comes with a significant hurdle- its Bill of Material (BOM) cost. The primary factors behind the situation being this way are:

  • N-Type Wafer Expenses: TOPCon Cells use N-Type wafers that contributes significantly to their higher BOM cost compared to PERC cells. N-Type wafers are generally more costly than their p-type counterparts, adding to the overall production expenses.
  • Increased Consumption of metallization pastes: Another reason for the high BOM cost is the increased consumption of metallized pastes in TOPCon Technology. As these pastes are very critical in cell’s construction and performance, it comes at a price, which further adds up because of increased usage in TOPCon cells.
  • Additional Processes like Tunnel Oxide Deposition: TOPCon Cells need additional processes such as tunnel oxide deposition, which further adds up to the BOM cost. While these added processes enhance the performance of the cell, it also contributes to the overall production expenses.