Researchers have developed a new manufacturing technique that can make high-performance solar panels more powerful – without making them significantly more difficult or expensive to produce.
By combining a specially developed silver paste with laser processing, the research team has improved a type of solar cell known as TOPCon (tunnel oxide passivated contact). The result was a certified efficiency of 26.31 percent – which places it among the best TOPCon cells reported so far.
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The research is led by Professor Ye Jichun’s team at the Ningbo Institute of Materials Technology and Engineering, affiliated with the Chinese Academy of Sciences. Together with collaborators from Soochow University, Zhejiang Gonda Electronic Technology and JA Solar Technology, they have now published the findings in the journal Matter.
The Challenge of Metal Parts
Crystalline silicon solar cells dominate the solar industry today, and TOPCon technology has become increasingly popular. One of the reasons is that manufacturers can use similar equipment and processes as for conventional silicon cells.
But there is a challenge: making the electrical metal contacts on the cells.
Manufacturers usually print a silver-aluminum paste on the cell and heat it to a high temperature. This creates good electrical connections that let the current out of the cell. But the intense heat and aluminum can damage the vulnerable surface layers that prevent energy loss. In addition, the metal lines can become wider, thus blocking more sunlight from reaching the cell’s active area.
How the researchers solved the problem
The researchers developed a new approach that solves both problems.
First, they made an aluminum-free silver paste with properties that allow it to retain its shape after printing. This makes it possible to produce taller and narrower metal lines. The resulting wiring networks achieved a height-to-width ratio of 55 percent – meaning they conduct electricity efficiently while covering less of the solar cell’s surface. Thus, more sunlight can hit the cell.
Next, the researchers combined the paste with a technique called laser-enhanced contact optimization (LECO). A laser scans along the metal structures while an electrical voltage is applied. This creates highly localized heating and establishes good electrical contacts at specific points.
Because the heating only happens where it is needed, much less of the solar cell’s protective surface structure is destroyed compared to conventional high-temperature processes.
Record results
The combination produced impressive results. The finished TOPCon cells achieved a certified efficiency of 26.31 percent. In addition, they measured a short-circuit current density of 41.98 milliamperes per square centimeter – which the researchers say is the highest certified value reported so far for large-field TOPCon solar cells.
Practical significance for the solar industry
The discovery could have great practical significance for the solar cell industry. Instead of sacrificing the protective properties of the cell to achieve good electrical contacts, the new paste and laser method provide both.
Because the approach is also designed to remain compatible with large-scale production, it could offer a practical path towards more efficient commercial solar panels – and ultimately more power from the same amount of sunlight.
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