First Commercial TOPCon Laser Carrier Paste From Solamet

Leading silver paste supplier Solamet announced that its solar paste, specifically developed for the TOPCon laser carrier injection technology, has been successfully utilized in mass production for over a quarter of the year at a leading PV manufacturer with stable results. The paste, named PV3NL, is the world’s first paste to achieve mass production with carrier injection technology adapted to the TOPCon cell architecture, claims the paste supplier. The paste is expected to improve the efficiency of both the simple TOPCon structure as well as the selective emitter TOPCon cell architecture by 0.2% absolute.

“One of the most significant technical challenges of TOPCon solar cells is the loss of open-circuit voltage and efficiency caused by the recombination issue caused by silver-aluminum pastes contacting p+ surface,” according to QJ Guo, Chief Technology Officer of Solamet. This can be addressed with laser induced carrier-injection technology, which is a post-treatment technology adopted on fired TOPCon solar cells. It employs laser to create high intensity carrier-injection to create more silver contact points to improve the ohmic contact with boron-doped p+ surface at a microcosmic level. The state–of–the–art aluminum doped silver paste cannot deliver the efficiency gain with the carrier-injection technology. 

Based on in-depth research into the mechanism on metallization induced recombination of the TOPCon p+ surface, Solamet has specifically designed the latest PV3NL solar paste to be integrated well with the laser carrier injection technology. It achieves a significant increase in open-circuit voltage, while maintaining good ohmic contact. As a result, an efficiency increase of more than 0.2% has been achieved on various TOPCon cell technologies. “Owing to the outstanding mitigation effect on metallization induced recombination of the new solar paste, this game-changing technology can assist in directing TOPCon or TOPCon SE cells towards ultra-high sheet resistance diffusion processes, unlocking greater potential for efficiency enhancement,” says Guo.

Adapting the laser carrier-injection technology using PV3NL paste does not require any big changes to the existing cell manufacturing process. In addition to increasing efficiency, the paste also increases module reliability, potentially addressing the industry’s challenge of TOPCon single-glass module reliability. Moreover, with its characteristics, PV3NL paves the way for future innovations in ultra-fine grid lines, low paste consumption, and low surface concentration diffusion processes for emitter regions.

“We are thrilled that Solamet is once again revolutionizing the photovoltaic industry with groundbreaking technology and product in its new chapter after independent operation following the previous acquisition of DuPont Solamet photovoltaic metallization pastes business”, according to Guo. Indeed the company has made several breakthroughs with respect to the emitter metallization of n-type cells. From introducing the industry’s first PV3N1 silver-aluminum paste for the n-type PERT cell p+ surface contacting in 2011, to pioneering the aluminum-free silver paste design concept in 2018, to introducing a new approach of high intensity carrier-injection to improve TOPCon metallization induced recombination and ohmic contact on p+ surface at the 8th Metallization Workshop in Changzhou, China in 2022, Solamet has been continuously researching ways to overcome the ohmic contact challenge with the p+ surface of N-type solar cells for more than a decade.