Solar cells based on iron molecules

Lund University researchers have explained how iron-based dyes work on a molecular level in solar cells. The ultimate goal of their study, published in the journal ChemSusChem Energy & Materials, is to be able to use iron-based dyes in solar cells.

As explained by study co-author Petter Persson, the researchers are looking for new opportunities to utilise solar energy in an inexpensive way. For some years now, scientists have been developing technology that uses a ruthenium dye molecule to harvest sunlight. “Unfortunately,” said Persson, “ruthenium is a very rare element.”

The Swedish researchers planned to use an iron-based dye molecule instead, with Persson stating, “Iron is very abundant on Earth; ruthenium, on the other hand, is something like 100 million times less common in nature.” By replacing ruthenium with iron, this would open the way for large-scale, inexpensive solar energy.

For decades, scientists have tried to develop iron-based dyes without success. A crucial reason for this difficulty is that achieving the right electronic properties in dyes based on iron is much more difficult compared to other metals. As noted by Persson, “Iron dyes have traditionally had a problem in that they are short-lived; they can’t keep the energy from the sun long enough to make this energy useful.”

However, the Lund researchers succeeded in creating molecules that are able to keep this energy for up to 100 times longer than previous iron dye molecules. “We can use this energy to shuttle electrons into an electrode,” said Persson. “This is the first step of generating an electric current.”

Persson said it will probably take a few years before iron dyes are used commercially in the production of solar cells and light catchers, stating, “To make a full solar cell requires some more development of these dye molecules.” He is, however, surprised at the rapid speed of development so far.

“It is difficult to develop new materials for solar energy conversion,” Persson said. “For once, the process has been unusually quick, and we have made several important breakthroughs in just a few years.”