A woven fabric-based interconnection technology for back-contact solar cells with possible integration of smart functionalities

Photovoltaics are gaining large interest due to the increasing demand for renewable energy. The biggest part of it is the silicon solar cell market, which can be divided into two main families. The first one is based on cells which have one polarity (- or +) at one side of the cell and the other polarity (+ or -) at the other side. The second group is based on solar cells where both polarities are brought to the backside of the cell, so-called back-contact cells. This latter group has many advantages over the first one, like the possibility to make full-black modules, higher efficiencies and possibilities to use them in curved modules. A major drawback is the lack of a standard method to interconnect the cells. This lack of standard interconnection makes them difficult and expensive to manufacture on an industrial scale. Imec proposes an innovative way of interconnecting these cells, based on a woven fabric. The fabric is composed of interwoven metal ribbons with solder coating as interconnecting material and polymer ribbons, which serve as encapsulation and electrical isolation material. The module manufacturing process consists of a layup step and a lamination step.

In the first step, the cells and woven fabric are aligned, and thus a stack is created. During the lamination step, the stack is heated under pressure, during which the solder melts and forms solder joints and simultaneously the polymer encapsulant melts and embeds the cells and interconnection.

The woven design can have an additional advantage for the power electronic system. Efficient power harvesting from photovoltaic modules is controlled by using power electronics. These devices are composed of switches (transistors) and passive magnetic components (inductors and capacitors) which are soldered on a PCB. The bulkiest components of the devices are the inductors. When these can be integrated into the PV module, power electronics reduces in volume, which facilitates the integration of all other components on a chip. This drastically lowers their manufacturing cost and improves their reliability.

The aim of this PhD project is to further develop this technology by investigating and controlling the polymer flow and adhesion behaviour, solder joint formation and the solar module characteristics.