Solliance reveals earth-friendly OPV production

Solliance, a cross-border research initiative on thin film photovoltaics by ECN, Holst Centre, Imec, TNO, TU Eindhoven and FZ Jülich, has claimed a world first with an inkjet printing process for developing environmentally friendly organic photovoltaic (OPV) cells that deliver benchmark efficiency. The process replaces toxic chlorinated solvents with more benign alternatives and is completely compatible with existing manufacturing technology, Solliance added.

OPVs promise cheaper solar cells that can be flexible, lightweight, semitransparent and easily integrated into construction materials. Until now, however, OPV production processes have relied on spin-coating techniques and chlorinated solvents. These solvents are highly toxic. Their potential for contaminating the water in rivers and killing wildlife making them a banned substance for industrial manufacturing processes. OPVs have so far been limited to lab-scale production.

Under its goal to eliminate toxic substances from production, Solliance has developed an OPV process that allows the photo-active layers to be inkjet printed without using poisonous chlorinates. The breakthrough was achieved in collaboration with French OPV manufacturer DisaSolar and within the framework of the European project X10D.

The 'magic' behind the process is a blend of low-toxicity solvents. They provide a stable base that achieves the right level of viscosity and surface energy of the inks, allowing OPVs to be printed. The resulting OPV cells deliver performances comparable to the spin-coated counterparts from standard chlorinated solvents, both achieving nearly three per cent efficiency for a P3HT:PCBM photoactive layer system.

Next to being environmentally friendly Solliance's solution also benefits from being based on inkjet printing, making it more suited to scaling up to commercial production. The process uses industrial print-heads, so cells are created in a single pass making production very fast.

"By combining a more environmentally friendly process with large area inkjet printing capability, we have successfully bridged the gap between academia and industry," said Tamara Eggenhuisen, research scientist in Solliance's organic photovoltaics programme.

"Apart from the speed and ecological advantages, using ink jet printing allows cells of any shape to be printed. As a result, OPV cells and modules could be fully integrated into building materials and other applications, adding invisible solar generation functionality for perfect environmental aesthetics," added Jan Gilot, senior research scientist in Solliance's organic photovoltaics programme.