Microwaves and phosphorus to increase solar cell efficiency

In a world in need of cheaper, more sustainable energy solutions, a simple and fast microwave experiment with the chemical element phosphorus has opened the door to more affordable and effective super-thin solar cells.

Flinders University nanotechnology researchers made flakes of phosphorene, a 2D form of phosphorus only a few atoms thick, in the hope of boosting the energy capacity of dye-sensitised solar cells (DSSC) — an emerging field of thin-film, semi-flexible and semi-transparent solar cells which are simple to make but limited by quite costly components such as platinum and ruthenium. Sheets and flakes of this phosphorus, just a few billionths of a metre thick, could improve the efficiency of this and other types of photovoltaic cells, the research team claims.

Solar cells based on carbon nanotubes and silicon promise a cheaper and easier-to-manufacture alternative to crystalline silicon cells. However, one challenge with these new solar cells is to boost their ability to effectively convert sunlight into electricity.

One approach is to include a layer of ultrathin nanoflakes of phosphorene, with the researchers hopeful that phosphorene has all the right properties to make it suitable for increasing solar cell efficiency. They prepared their phosphorene by immersing phosphorus in a special liquid and exposing it to microwaves for 10 minutes — in contrast to previous protocols involving 15 hours of heating.

In a study published in the journal Angewandte Chemie, the team used the phosphorene to fabricate DSSC, which showed photovoltaic efficiency of 8.31% — outperforming expensive platinum-based cells and thus potentially removing the need to include their most costly component.

In a second study, published in Advanced Function Materials, the team again used the microwave method to make phosphorene flakes and then added them to carbon nanotube–silicon solar cells to show a significant improvement in the cells’ power conversion.

A third study, published in Small Methods, showed that the team’s suspended phosphorus sheets showed good stability, while samples dispersed onto silicon from the suspensions exhibited low oxidation levels after several days in ambient conditions.

“With these promising early results, further studies with the microwave technique and other solvents will help improve stability and durability of phosphorene and allow us to look at ways to produce larger amounts of phosphorene for possible commercial applications,” said Dr Christopher Gibson, a co-author on all three studies.

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