Laser-Based Contacting Process For Solar Cells

• Fraunhofer ISE and industry partners have developed a new process to produce solar cell contacts
• The LTF technique is a 2-step process which enables higher solar cell efficiencies, the team claims
• The experiment was successfully accomplished in the lab as well as on an industry scale system
• ISE now believes the technology is ready to be systematically tested and optimized for industrial implementation

Fraunhofer Institute for Solar Energy Systems (ISE) says it has developed an alternative process called laser transfer and firing (LTF) technique to produce solar cell contacts calling it C3PO Project. It offers several advantages over conventional processes, especially for specific solar cell surfaces, says the German research and testing institute.
Having previously carried out the experiment successfully in a laboratory setting, the Fraunhofer ISE team and partners have now developed this process on an industry scale system. Researchers here claim the process can be systematically tested and optimized for industrial implementation.
Fraunhofer ISE worked on the project along with its industry partners, namely Pulsar Photonics GmbH that provided its laser machine for the project; customized coating systems specialist ROWO Coating that specifically developed the coated films for this project, crystalline silicon solar cell production equipment company RENA Technologies GmbH, and laser source supplier Soliton Laser- und Messtechnik GmbH.
The German Federal Ministry for Economic Affairs and Energy (BMWi) funded project experiments with the use of an alternative material apart from nickel to create the metal contact fingers by using aluminum, titanium or bismuth and this it does by opening the insulating layer to create the metal contact fingers.
As per the team, of the 2 steps in the LTF process, the 1^st step involves a direct laser printing process to transfer metal in the desired contact finger layout from a metal-coated foil to a solar cell calling this step as Laser Induced Forward Transfer (LIFT). The solar cell is placed on a vacuum chuck and moved under a metal coated foil—prepared for this project by ROWO—and automatically transported through a roll-to-roll system for the metal transfer of the next solar cell.
The 2^nd step used metal structures from step 1 and to create into contacts using a laser selective heating (LSH) process created by Soliton. The team claims in this step the laser does not harm the silicon material since the wavelength of the beam is absorbed only by the metal and not by the silicon underneath. This can lead to higher solar cell efficiencies, it adds.
"In addition to the manufacture of minuscule 3D structures and the localized coating of sensitive components, we see possible applications for the LTF technology in a variety of other research fields. With the pilot system and our consortium of experts, we hold the best prerequisites to successfully develop these in the future," said Jan Nekarda, Department Head of Structuring and Metallization at Fraunhofer ISE, .
Last month, Fraunhofer ISE introduced its new spin-off calling it HighLine Technology to commercialize a contactless solar cell dispensing printing process (see Fraunhofer ISE Spin-Off For Solar Cell Production).