Solar cell efficiency boosted by bio-material

24 Oct 2019

Research at Penn State University finds that adding protein to perovskite cells significantly raises conversion efficiency.

Adding the protein bacteriorhodopsin (bR) to perovskite solar cells has been found to boost the efficiency of these so-called “photosynthesis-mimicking” solar cells, say researchers at Penn State University, University Park, PA.

“These findings open the door for the development of a cheaper, more environmentally friendly bioperovskite solar cell technology,” said Shashank Priya, associate VP for Research and professor of materials science. “In the future, we may replace certain expensive synthetic chemicals in solar cells with relatively cheaper natural materials.”

The Penn State Group’s work has recently been reported in the American Chemical Society journal Applied Materials and Interfaces.

The most efficient perovskite solar cells can convert 22 to 23 percent of sunlight power into electricity. The researchers found that adding the bR protein to perovskite solar cells improved the devices’ efficiency from 14.5 to 17 percent.

They say that this research represents the first time scientists have shown that biological materials added to perovskite solar cells can provide a high efficiency. Future research could result in even more efficient bioperovskite materials.

“Previous studies have achieved 8 or 9 percent efficiency by mixing certain proteins inside solar cell structures,” said Priya, a co-lead author of the study. “But nothing has come close to 17 percent. These findings are very significant.”

Mimicking nature

The researchers, who commented that they were “drawing on nature”, were seeking to improve the performance of perovskite solar cells through Förster Resonance Energy Transfer (FRET) – a mechanism for energy transfer between a pair of photosensitive molecules.

“The FRET mechanism has been around for a long time," commented Renugopalakrishnan Venkatesan, professor at Northeastern University and Boston Children's Hospital, Harvard University, and co-lead author on the study. "It seems to be the basis of photosynthesis and we are using this mechanism to try to create a world of bio-inspired systems that have the potential to surpass either inorganic or organic molecules.”

The bR proteins and perovskite materials have similar electrical properties, or band gaps. By aligning these gaps, the scientists hypothesized they could achieve a better performance in perovskite solar cells through the FRET mechanism.

“Solar cells work by absorbing light energy, or photon molecules and creating electron-hole pairs,” said Subhabrata Das, who participated in the research while a doctoral student at Columbia University. “By sending the electrons and holes in opposite directions, solar cells generate an electrical current that’s turned into electricity.”

However, a certain percent of electron-hole pairs recombine, reducing the amount of current produced. Mixing the bR protein into perovskite solar cells helped electron-hole pairs better move through the devices, reducing recombination losses and boosting efficiency, the scientists said.

The findings could potentially have larger consequences, leading to the design of other hybrid devices in which artificial and biological materials work together, according to the researchers. Bernardo Barbiellini, professor at the University of Lappeenranta, Finland, also served as co-lead author of the study.