Standard soldering techniques applied to large and thin silicon solar cells can lead to cell breakage because of mechanical stresses. Several alternative stress-free interconnection technologies have been explored: mechanical contacting and physical joining by means of electrically conductive adhesives. A mechanical contacting technology relying purely on contact pressure exerted by magnets was investigated. This technology is truly stressfree because there is no means of physical joining of the tabs with the cell. Durable contacts can be manufactured using this technique. It was shown however, that this method does not give reliable results after EVA encapsulation. The EVA encapsulant underflows the tab which leads to unstable contact resistances. Interconnection with conductive adhesives performs excellently. Recent development of flexible conductive adhesives has greatly increased the reliability of the adhesive bond. Low process temperatures lead to low-stress interconnections with excellent mechanical properties, conductivity and durability.

The simplest way to produce a module of crystalline silicon solar cells is with back-contacted cells that are glued on an interconnection foil using conductive adhesives. This foil also serves as environmental barrier at the rear of the module. The conductive adhesive is tuned to cure in the same cycle as the encapsulant. It is possible to interconnect the cells without any additional temperature curing in a single lamination step. The interconnection foil can be made for an acceptable cost price, as is shown in the paper. The savings in labor, a higher efficiency, and a yield increase will lead to a lower cost price for such a module. First results show that a module produced in a single step leads to similar fill factors as soldered modules.

Thin crystalline silicon solar cells cannot be interconnected with standard soldering techniques because of warping and breakage. Interconnection with conductive adhesives showed excellent behavior: warping can be avoided and 80μm thin cells do not break during and after interconnection. Contact resistances measured on glued interconnections are similar to soldered contacts. Damp/heat tests show no degradation after 2500 hours at 85°C/85% humidity. Temperature cycling –40/+80°C has shown no effects after 200 cycles. I-V measurements of interconnected thin back-contact cells in mini modules show no loss in fill factor. Test mini modules made with soldered back contacts and glued front contacts show excellent performance even after over 900 cycles. Interconnection with conductive adhesives is a promising technique combining excellent mechanical properties, good conductivity, durability, and low process temperatures thus reducing stress.

Thin crystalline silicon solar cells cannot be interconnected with standard soldering techniques because of warping and breakage. Interconnection with conductive adhesives showed excellent behavior warping can be avoided and 80mum thin cells do not break during and after interconnection. Contact resistances measured on glued interconnections are similar to soldered contacts. Damp/heat tests show no degradation after 2500 hours at 85degreesC/85% humidity. Temperature cycling -40/+80degreesC has shown no effects after 200 cycles. I-V measurements of interconnected thin back-contact cells in mini modules show no loss in fill factor. Test mini modules made with soldered back contacts and glued front contacts show excellent performance even after over 900 cycles. Interconnection with conductive adhesives is a promising technique combining excellent mechanical properties, good conductivity, durability, and low process temperatures thus reducing stress.

Presents an outline of the work done in the EC co-funded project ACE Designs. The objective of this project was to develop rear contact solar cell designs and to demonstrate their applicability as an alternative crystalline silicon technology for industrial module production. An overview of the results is given with links to the most relevant, publications for further details. The most important result of this project was that rear contact solar cells are a feasible, attractive and cost effective alternative to the well-known front contacted solar cell.

An alternative way for producing PV modules is presented. These modules are equipped with back- contacted cells connected to an interconnection foil by means of electrically conductive adhesives. The interconnection foil is a modification of standard back-sheet foil. The conductive adhesive is cured together with the EVA encapsulant, which implies a single-shot interconnection and lamination cycle. The savings in labor, reduction of machine equipment and a higher module efficiency lead to a reduction of the €/Wp price. Measurements show that modules can be produced with a higher power output when compared to modules using soldered standard cells. Outdoor test results show the viability of the concept.