The Army Research Office and the Office of Naval Research have provided financial support for a new perovskite research, along with the National Science Foundation and the Energy Department's Office of Science. The researchers are a team of engineers working out of the lab of Aditya Mohite at Rice University.
The project was a collaborative one that also involved Purdue and Northwestern universities. The Energy Department was also involved via its Los Alamos, Argonne and Brookhaven laboratories. So were the Institute of Electronics and Digital Technologies in France, with additional support from the Academic Institute of France.
The team built their new 2D perovskite solar cell on previous research indicating a pathway for balancing durability with efficiency. 'We've been working for many years and continue to work with bulk perovskites that are very efficient but not as stable. In contrast, 2D perovskites have tremendous stability but are not efficient enough to put on a roof,' explains Mohite.
Recent iterations of perovskite solar technology have added 2D structures to enhance stability. The Rice team decided to do away with the 3D 'bulk' structure and go straight for the 2D.
'We find that as you light the material, you kind of squeeze it like a sponge and bring the layers together to enhance the charge transport in that direction,' said Mohite. 'This effect has given us the opportunity to understand and tailor these fundamental light-matter interactions without creating complex heterostructures like stacked 2D transition metal dichalcogenides,' he added.
The actual amount of squeezing is minuscule, but it apparently makes a big difference. After exposure to a solar simulator, the team's perovskite lattice contracted about 0.4% lengthwise and 1.0% vertically.
'It doesn't sound like a lot, but this 1% contraction in the lattice spacing induces a large enhancement of electron flow,' said co-lead author Wenbin Li, who is a Rice Applied Physics graduate student. 'Our research shows a threefold increase in the electron conduction of the material.'
The lattice also quickly resumed its normal shape after the light was removed, indicating improved durability compared to 3D versions.
'We're on a path to get greater than 20% efficiency by engineering the cations and interfaces,' Sidhik explains. 'It would change everything in the field of perovskites, because then people would begin to use 2D perovskites for 2D perovskite/silicon and 2D/3D perovskite tandems, which could enable efficiencies approaching 30%.'