Scientists from Solliance, the cross-border thin-film solar cell research alliance, have produced the world's first organic photovoltaics (OPVs) to be made exclusively with inkjet printing processes. The processes offer complete flexibility of cell shape, substrate and structure, so are ideal for rapid product development and prototyping. Moreover, they enable easy up-scaling to volume manufacturing of cost-effective products.
OPVs promise low-cost solar cells that can be made in different colors and can be flexible, lightweight, semitransparent, made in different colors and easily integrated into construction materials. This latest development from Solliance makes it quicker and easier for manufacturers to explore the various technical options for new products and then transfer successful prototypes to production.
Solliance created single-junction OPVs made up of a six-layer stack. All six layers were produced using industrial inkjet printing at roll-to-roll compatible speeds. To make this possible, the researchers developed new ink formulations and optimized process control for each layer to avoid solvents from one layer re-dissolving already deposited layers.
"With industrial inkjet printing, manufacturers can switch between making different shapes of cells and modules at any time during production. It is equally as easy to switch between opaque or semitransparent, and bottom-absorbing or top-absorbing cells. And because it is a low-temperature process they can use any substrate they like: glass, plastic films or metal foils. This kind of flexibility is perfect for a technology that is still being explored," explains Tamara Eggenhuisen, research scientist in Holst Centre's Large Area Printing program.
The all-inkjet-printed OPVs were created with standard, affordable materials. They are free of indium-tin-oxide (ITO), further reducing production costs and the use of scarce raw materials such as indium. Furthermore, only 4 types of ink are required to produce the complete six-layer stack, simplifying the sourcing of materials. Additional junctions can be included to boost the electricity output of the cell simply by adding three extra layers using only one additional ink per junction.
"Inkjet printing is a well-established technology in industries such as textile and graphics printing. It offers a simple route to industrialization, allowing customizable production at high volumes. What's more, inks developed for inkjet printing can be used for slot-die and spray coating with no extra development, giving manufacturers greater freedom of choice in the high-volume production technology they use," adds Ronn Andriessen, Organic Photovoltaics program manager at Solliance.
See a video of the all-inkjet-printed OPV on the Holst Centre YouTube channel.