Rice University scientists have made use of inorganic ingredients to limit the defects affecting perovskite solar cells.
The team led by Rice materials scientist Jun Lou have made use of the element ‘indium’ to replace some of the lead in perovskites.
This helped them solve some of the defects in cesium-lead-iodide solar cells that affect the compound’s band gap – a critical property in solar cell efficiency.
According to the scientists, their newly formulated cells can be made in open air and last for months rather than days with a solar conversion efficiency slightly above 12%.
“From our perspective, this is something new and I think it represents an important breakthrough,” says Lou.
“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.”
As part of their research, lead author Jia Liang and his team built and tested perovskite solar cells of inorganic cesium, lead and iodide which tend to fail quickly due to defects.
But by adding bromine and indium, the researchers were able to quash defects in the material, raising the efficiency above 12% and the voltage to 1.20 volts.
The material has also proven to be exceptionally stable: The cells were prepared in ambient conditions and once encapsulated, they remained stable in air for more than two months.
“The highest efficiency for this material may be about 20%, and if we can get there, this can be a commercial product,” notes Liang.
“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.”
Image and content: Jeff Fitlow/Rice University