| Work Detail |
Researchers at the German Fraunhofer ISE institute have developed new techniques to reduce silver consumption in tandem perovskite silicon solar cells and heterojunction silicon photovoltaic devices. The new processes are related to the metallization of cells and the interconnection of modules.
Researchers at the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) have developed new low-temperature manufacturing processes for perovskite silicon tandem cells and heterojunction solar cells. New techniques make it possible to reduce silver consumption and avoid soldering materials that contain lead.
“We demonstrate that, with a deep knowledge of the processes and behavior of the materials, low-temperature metallization and interconnection with the established equipment of the solar cell and module production lines is possible,” the author told pv magazine . principal of the investigation, Angela De Rose.
The scientists developed two different processes: front face metallization at very low temperatures for full-size perovskite silicon tandem solar cells; and interconnection with high-efficiency full-format demonstration modules with an output power of more than 400 W.
Fine line screen printing was used in the metallization stage. The selected paste proved suitable for reliable high-speed printing with widths of 20 µm, resulting in a printed width of 26 µm. The process resulted in 43% less silver consumption compared to tracing with 35 µm finger widths. According to the researchers, curing at 150ºC allowed for “good electrical properties” and high-throughput production thanks to fast curing times of up to 2 minutes per wafer.
For interconnection, the group used electrically conductive adhesives (ECA), examining various pastes and methods. “There are many ECAs available on the market, which allow processing at different temperature ranges, including less than 200ºC and less than 150ºC,” they explain, noting that most ECAs use silver particles to ensure greater electrical conductivity. .
Their techniques managed to reduce silver by using finer line printing and less ECA than conventional methods and avoiding lead-containing materials in low-temperature screen printing pastes and lead-free solder alloys.
The researchers claim that they have been able to use 50% less ECA compared to conventional continuous application patterns, and note that the proposed solution offers sufficient joint adhesion for chain handling and stable modulus powers in the cells, also for ECA curing temperatures of 130 ºC. “The main challenge of this approach is to keep the curing time as short as possible to allow high performance,” they say.
The solar modules manufactured with a soldered wire interconnect and an ECA tape interconnect have a total area of ??1.8 m2, a power of more than 400 W and consist of full-size perovskite silicon tandem half cells. According to the researchers, the solder-coated wire allowed for low-temperature processing and damage-free manufacturing.
“Thanks to the joint optimization of the processes and materials involved, we have been able to build high-efficiency perovskite silicon heterojunction modules in full format with different interconnection technologies,” says De Rose.
The team claims the process enables high-throughput production at chaining rates of 1,600 to 1,800 cells per hour. The cellular matrix, silicon heterojunction or tandem, was embedded in a commercially available encapsulant for a lamination process within a conventional process window between 140 °C and 160 °C. The full-size modules were constructed as glass-glass modules with edge sealing.
The processes are described in the study “ Low-temperature metallization & interconnection for silicon heterojunction and perovskite silicon tandem solar cells ,” published in Solar Energy Materials and Solar Cells .
Future research activities of the group include low-temperature lead-free soldering, shingling interconnection using ECA, as well as long-term stability of tandem cells and modules. |
