Module Technology

Interconnection and Encapsulation of Tandem Solar Cells

At Fraunhofer ISE we are researching and developing reliable solutions for the interconnection and encapsulation of silicon perovskite tandem and III-V silicon tandem solar cells. Due to the different characteristics of tandem solar cells, the conventional interconnection and encapsulation processes used for c-Si solar cells cannot be transferred one-to-one to the different tandem technologies. For example, silicon perovskite tandem solar cells are particularly sensitive to humidity, temperature and mechanical stress. III-V/silicon tandem solar cells are thin and flexible. Fraunhofer ISE is thus developing various interconnection processes such as shingling for silicon III/V tandem solar cells. This allows the minimization of cell-to-module losses, making very high module efficiencies possible. Our development work is accompanied by an in-depth characterization based on simulations and measurements. 

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For silicon perovskite tandem solar cells, we are developing several interconnection methods, e.g. conductive bonding, wire interconnections based on SWCT (Smart Wire Connection Technology), and low temperature soldering. We also develop low-temperature processes and materials for the encapsulation of silicon perovskite tandem solar cells with a special focus on reliable edge sealing. Drawing on many years of experience, we have the knowledge when it comes to meeting the requirements for reliability, electrical performance and low manufacturing cost. Our modern industrial infrastructure contains state-of-the-art equipment such as an adhesive stringer, wire stringer, SWCT stringer, laminator, etc. which allow us to develop a wide range of products.  Aside from this, we develop equipment, connectors and adhesives with our industrial partners.

We also develop encapsulation materials and processes for III/V tandem solar cells. For instance, we were also able to develop a PV module with a weight of just 380 g/m² (the classical silicon module is about 10,000 g/m²). Such lightweight modules are particularly relevant for aerospace applications.

Interconnected shingle solar cells
© Fraunhofer ISE
Interconnected shingle solar cells on a structured encapsulating foil, optimized for the SlimLine process.
Automated cell interconnection on industrial cell stringer
© Fraunhofer ISE
Automated cell interconnection on industrial cell stringer in Module-TEC Module Technology Evaluation Center.
Shingled solar cells in matrix structure
© Fraunhofer ISE
Shingled solar cells in matrix structure achieve a very high efficiency.

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