This electron microscope image shows a cross-section of the all-inorganic perovskite solar cell developed at Rice University. From top, the layers comprise a carbon electrode, perovskite, titanium oxide, fluorine-doped tin oxide and glass; the scale bar is 500nm. Image: Lou Group/Rice University.Scientists at Rice University believe they've overcome a major hurdle that is preventing perovskite-based solar cells from achieving mainstream use.
By replacing some of the lead in perovskites with indium, Rice materials scientist Jun Lou and his colleagues at the Brown School of Engineering say they're better able to engineer the defects in cesium-lead-iodide solar cells that can affect the compound's band gap, a critical property in solar cell efficiency. As a side benefit, the lab's newly formulated cells can be made in the open air and last for months rather than days with a solar conversion efficiency slightly above 12%. The Rice team report their results in a paper in Advanced Materials.
Perovskites are crystals with cubelike lattices that are known to be efficient light harvesters, but the materials tend to be stressed by light, humidity and heat. Not the new Rice perovskites, though, according to Lou.
"From our perspective, this is something new and I think it represents an important breakthrough," he said. "This is different from the traditional, mainstream perovskites people have been talking about for 10 years – the inorganic-organic hybrids that give you the highest efficiency so far recorded, about 25%. But the issue with that type of material is its instability.
"Engineers are developing capping layers and things to protect those precious, sensitive materials from the environment. But it's hard to make a difference with the intrinsically unstable materials themselves. That's why we set out to do something different."
Rice postdoctoral researcher and lead author Jia Liang and his team built and tested perovskite solar cells made of inorganic cesium, lead and iodide, the very cells that tend to fail quickly due to defects. But by adding bromine and indium, the researchers were able to quash defects in the perovskite, raising the efficiency above 12% and the voltage to 1.20 volts.
As a bonus, the modified perovskite proved to be exceptionally stable. The solar cells could be prepared in ambient conditions, standing up to Houston's high humidity, and encapsulated cells remained stable in air for more than two months, far better than the few days achieved by plain cesium-lead-iodide cells.
"The highest efficiency for this material may be about 20%, and if we can get there, this can be a commercial product," Liang said. "It has advantages over silicon-based solar cells because synthesis is very cheap, it's solution-based and easy to scale up. Basically, you just spread it on a substrate, let it dry out, and you have your solar cell."
This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.