Bulky molecule makes more stable perovskite solar cells

Perovskite is quickly emerging as a frontrunner for more efficient solar cells, but it has one major problem – it’s a bit too fragile. Now, a team of engineers led by Purdue University has found that adding one bulky molecule can stabilize the material, making it stackable in layers and opening up its usefulness in solar cells and other electronics.

Conventional solar cells are made with silicon in the active layer, and after decades of refinement these devices have reached efficiencies of over 20 percent. Perovskite solar cells, meanwhile, have advanced to around the same level in just 10 years. When paired up, silicon and perovskite reach efficiencies as high as 27.7 percent.

The added bonus of perovskite is that the material is also easier and cheaper to produce in bulk, and is so thin that it can be printed or sprayed onto surfaces.

But, of course, there’s a catch. Perovskite is notoriously unstable, so it’s vulnerable to the elements – which isn’t great considering solar cells are out there in the Sun and rain all day – and it doesn’t stack well in layers.

For the new study, the researchers found a fairly simple way to make halide perovskite more stable. They added a rigid, bulky molecule called bithiophenylethylammonium to the surface of perovskite. This stabilizes the movement of ions, which the team says prevents the chemical bonds of the material from breaking apart too easily, or mixing with other layers of perovskite materials.

“If an engineer wanted to combine the best parts about perovskite A with the best parts about perovskite B, that typically can’t happen because the perovskites would just mix together,” says Brett Savoie, an author of the study. “In this case, you really can get the best of A and B in a single material. That is completely unheard of.”

The team also demonstrated that adding the molecule made the perovskite stable in temperatures as high as 100 °C (212 °F). That’s important for something that needs to be in direct sunlight, and could make it useful in electronic devices too. The researchers suggest that perovskites could be put to work in transistors, for example.

The research was published in the journal Nature.

Source: Purdue University

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