Iodide-Missing Defects Found to Degrade Perovskites

Perovskites have shown great promise for making flexible and cheap solar cells. However, so far researchers have been unable to overcome one big issue, they degrade rapidly in natural conditions. In fact, exposure of perovskites to natural conditions greatly decreases their performance in just days. However, scientists from Imperial College, London discovered that iodide-missing defects may be the cause.

Previously, a group led by researchers from the Department of Chemistry at Imperial College, London learned that this rapid degradation is the result of the formation of a ‘superoxide’ that corrupts the perovskite material. When light hits the cells and releases electrons, these superoxides form and react with the oxygen content of the air.

Now, working with Saiful Islam and Christopher Eames at the University of Bath, the team discovered that spaces in the perovskite structure usually taken up by molecules of iodide aid superoxide formation. While iodide is a component of the perovskite material, defects in the structure are missing iodide. Then, the formation of superoxides uses these vacant spots.

The team found adding extra iodide after manufacturing improved the stability. The findings were published in Nature Communications.

The team speculates that engineering the defects out might offer a more permanent solution. While one solution for protecting perovskite material from the air is encasing it in glass, this considerably reduces the flexibility of the material and severely limits its uses.

Next, the team intends to test the stability of the cells in real-world conditions with exposure to both oxygen and moisture.

 

Reference

Nicholas Aristidou et al. ‘Fast oxygen diffusion and iodide defects mediate oxygen induced degradation of perovskite solar cells’. Nature Communications 8 15218 (2017). doi:10.1038/ncomms15218