Adding one more layer of metal fluoride can enhance performance of solar cells

Researchers at KAUST have found that adding a metal fluoride layer in tandem solar cells can improve performance.

The combination of perovskite and Silicon-based subcells in one device is expected to better capture and convert sunlight into electricity than their conventional single-junction Silicon analogs at a lower cost. The resulting pairs of electrons and positively charged holes tend to recombine at the interface between the two layers. There is a mismatch between energy levels at this interface. The problems lower the maximum operating voltage available and limit device performance.

The performance issues can be partially solved by introducing a lithium fluoride layer between the two layers. The devices are unstable due to the liquification and diffuseness of the salts. "None of the devices have passed the standard test protocols of the International Electrotechnical Commission, prompting us to create an alternative," says JiangLiu, a post-doc in the group.

The potential of other metal fluorides, such as magnesium fluoride, as interlayer materials was investigated by the co-workers. They added C 60 and top contact components to create an ultrathin uniform film. In line with inverted p-i-n solar cell requirements, the interlayers are transparent and stable.

The interlayer of magnesium fluoride promoted the removal of electrons from the active layer. The charge was reduced at the interface. Charge transport was increased across the subcell.

One of the highest efficiency tandem solar cells on the market was achieved by the resulting tandem solar cell.

This innovative technology could bring considerable performance gains without adding to the cost of fabrication if it were not for the fact that the best efficiency is 26.7 percent.

In order to explore the applicability of this technology, the team is developing methods to produce industrial-scale perovskite-Silicon tandem cells with areas greater than 200 square centimeters. Highly stable tandem devices that will pass critical industrial stability protocols are being developed.

More information: Jiang Liu et al, Efficient and stable perovskite-silicon tandem solar cells through contact displacement by MgF_x, Science (2022). DOI: 10.1126/science.abn8910 Journal information: Science