Solar cell technology used to manufacture photovoltaic (PV) modules is constantly evolving as new, more advanced and more efficient technologies are developed. Tunnel oxide passivated contact (TOPCon) solar cell technology is a new development with the potential to replace passivated emitter and rear contact (PERC) and high-efficiency passivated emitter, rear totally-diffused (PERT) solar panels.

TOPCon solar cell technology is one of the latest trends in the solar industry, developed as an upgraded and more advanced version of the PERC/PERT technology. One of the main advantages of TOPCon solar cells is that the structure is only slightly different from PERC/PERT solar cells, meaning that manufacturers can use practically the same production line with a few improvements to produce TOPCon solar cells. It was first introduced as a concept in 2014 by the Fraunhofer ISE German PV research institute. The project designed to develop this technology took place from 2013 to 2016, but it was not until 2019 that companies like Trina Solar scaled it to production. As TOPCon solar cell technology proved as a successful upgrade from PERC solar cells, many other companies including LONGi Solar, Suntech, Canadian Solar, and many others got interested in it.

The main setback of this new technology compared to PERC/PERT is that the TOPCon solar cells require a larger amount of silver (Ag) for production. This silver increase translates into a higher manufacturing price; however, new developments might prove successful in reducing the required amount of silver, while still delivering similar or even higher efficiencies and reducing production costs.

TOPCon solar cells can be manufactured as n-type or p-type solar cells, but the n-type variation has proven to be more efficient and resistant to impurities. Because TOPCon solar cells are an upgrade from PERC/PERT solar cells, it is important to understand the structure of this new technology.

PERT solar cells are manufactured with an n-type crystalline silicon (c-Si) bulk layer because of its higher surface quality and it is coupled with a p+ emitter layer to create the p-n junction. The emitter layer is covered with an aluminum oxide (Al2O3) passivating layer and topped with a silicon nitride (SiNx) coating for its anti-reflecting properties. PERC solar cells replace the absorber layer with a p-type bulk layer and an n+ emitter for the p-n junction.

The lower part of the bulk region is doped with phosphorous to create the back surface field, and it is then coated with SiNx similar to the top of the cell. Both the top and bottom of the solar cell are equipped with silver (Ag) or aluminum (Al) contacts to close the circuit when the cell is being connected to the load or other cells at the time of manufacturing the PERC/PERT solar panel.

The TOPCon solar cell structure takes the base structure of the PERT solar cell but includes an ultra-thin silicon dioxide (SiO2) layer working as the tunnel oxide layer and replaces the back surface field layer with phosphorous-doped polycrystalline silicon (n+ Poly-Si) layer. These modifications have improved the efficiency by reducing the recombination process thanks to the passivation in the added layers.

TOPCon solar cell technology is quite promising, having the potential to rapidly grow within the solar industry. When considering a new rising technology like this one, it is important to analyze it against other popular PV technologies in the market. In this case, we will compare TOPCon solar cell technology against PERC and heterojunction (HJT) solar cell technologies.

PERC solar cell technology currently sits in the first place, featuring the highest market share in the solar industry at 75%, while HJT solar cell technology started to become adopted in 2019, its market share was only 2.5% by 2021. TOPCon, which is barely present in the market, already represents 8% of the PV market, but it might start to grow in 2023 as major manufacturers switch from PERC/PERT to TOPCon.

TOPCon solar cell technology is a revolutionizing product that upgrades the design of the PERC/PERT solar panels. The solar industry is starting to get acquainted with TOPCon solar cell technology. LONGi already launched its bifacial modules in 2021, but most manufacturers will be releasing their high-efficiency TOPCon solar panels from the second (Q2) to the last quarter (Q4) of 2023.

It is possible that at first, TOPCon solar cell technology will have slightly more expensive costs than PERC/PERT solar panels, but analysts expect that the cost for TOPCon solar panels will fall lower than the current cost of PERC solar cell technology.

The path for TOPCon solar cell technology is also not entirely free from competition. There are other technologies featuring an interesting great potential to go against this newly upgraded technology, including HJT as it is further developed, and interdigitated back-contacted (IBC) solar cell technology.

*** Source: SOLAR Magazine ***