Scientists have developed a new manufacturing technique that could help make high-efficiency solar panels more powerful without making them much harder or more expensive to produce.
The researchers used a combination of a specially designed silver paste and laser treatment to improve a type of solar cell known as a tunnel oxide passivated contact, or TOPCon, solar cell.
Their device reached a certified power conversion efficiency of 26.31%, putting it among the highest-performing TOPCon solar cells reported so far.
The research was led by Professor Ye Jichun’s team at the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences.
The team worked with researchers and industry partners from Soochow University, Zhejiang Gonda Electronic Technology, and JA Solar Technology.
The findings were published in the journal Matter.
Crystalline silicon solar cells dominate today’s solar industry, and TOPCon technology has become increasingly popular. One reason is that manufacturers can produce TOPCon cells using equipment and processes similar to those already used for conventional silicon solar cells.
However, making the metal electrical contacts on these cells presents an important challenge.
Manufacturers commonly print a silver-aluminum paste onto the solar cell and then heat it to a high temperature. This creates good electrical connections that allow electricity to flow out of the cell.
But the intense heat and aluminum can damage the delicate surface layers that help prevent electrical energy from being lost. The metal lines can also become wider, blocking more sunlight from reaching the active area of the solar cell.
The researchers developed a way to tackle both problems.
First, they created an aluminum-free silver paste with properties that allow it to maintain its shape after being printed. This makes it possible to produce taller and narrower metal lines. The resulting gridlines achieved an aspect ratio of 55%, meaning they can conduct electricity efficiently while covering less of the solar cell’s surface. More sunlight can therefore enter the cell.
The scientists then combined the paste with a technique called laser-enhanced contact optimization, or LECO. A laser scans along the metal gridlines while an electrical voltage is applied. This creates highly localized heating and helps establish good electrical contacts at specific points.
Because the heating is concentrated only where it is needed, much less of the solar cell’s protective surface structure is damaged compared with conventional high-temperature processing.
The combination produced impressive results. The finished TOPCon solar cells reached a certified efficiency of 26.31%. They also achieved a short-circuit current density of 41.98 milliamps per square centimeter, which the researchers say is the highest certified value reported so far for large-area TOPCon solar cells.
The advance could have practical importance for the solar industry. Instead of sacrificing the cell’s protective properties to obtain good electrical contacts, the new paste-and-laser method provides both.
Because the approach is also designed to remain compatible with large-scale manufacturing, it could offer a practical route toward producing more efficient commercial solar panels and ultimately generating more electricity from the same amount of sunlight.
