Army and Navy lend muscle to perovskite solar cell

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The US Department of Defense is committed to a climate action posture, which includes support for new clean technologies. In the latest development, the military and navy lent their financial firepower to a new 2D perovskite solar cell research project. If all goes according to plan, the result will be a lightweight, inexpensive and highly efficient solar cell that can deliver clean kilowatts over a lifespan of 20 to 25 years.

Perovskite solar cell to the rescue

For those of you new to the subject, perovskite is a natural mineral with unique optical properties that make it ideal for photovoltaic applications.

Perovskite solar cell research only began in earnest about 10 years ago, with the US Department of Energy among those chasing it. The results have been impressive. The solar conversion efficiency of a solar cell to perovskite increased from 3% to over 25% during this 10-year period. In contrast, current solar cell semiconductors have taken around 60 years to reach the 25% benchmark.

To brown the clean tech lily, synthetic crystalline materials that mimic perovskite are relatively easy and inexpensive to grow.

Army and Navy join 2-D perovskite solar cell team

Since a free lunch does not exist, “raw” perovskite tends to fall apart when exposed to moisture and sunlight. This complicates things for the R&D phase, but it is not an insurmountable problem. Researchers have already found a series of workarounds that can bring perovskite solar cells to market.

The remaining conundrum is how to enhance the durability of a perovskite solar cell without sacrificing the efficiency of solar conversion.

This brings us to the Army-Navy mashup, which helped create the mother of all workarounds: a two-dimensional perovskite solar cell formula that gains durability and efficiency when exposed to the sun, instead of losing it. .

The Army Research Office and the Naval Research Office have provided financial support for new perovskite research, as have the National Science Foundation and the Department of Energy’s office of science.

Much of the work was done by a team of engineers working in Aditya Mohite’s lab at the George R. Brown School of Engineering at Rice University. Here, let Rice explain:

“Aditya Mohite’s lab at the George R. Brown School of Engineering in Rice discovered that sunlight itself sufficiently contracts the space between atomic layers in 2D perovskites to improve the photovoltaic efficiency of the material up to ‘to 18%, an incredible leap in an area where progress is often measured in fractions of a percent.

For the record, the project was a collaborative project that also involved Purdue and Northwestern universities. The Department of Energy also helped with a helping hand from its Los Alamos, Argonne and Brookhaven labs. Assistance from the French Institute of Electronic and Digital Technologies has made it an international affair, with additional support from the Institut universitaire de France.

The 2D perovskite PV solution: how it works

The Rice team built their new 2D perovskite solar cell based on previous research showing a way to balance sustainability and efficiency.

“We have been working for many years and continue to work with bulk perovskites which are very effective but not as stable. In contrast, 2D perovskites have enormous stability but are not efficient enough to be placed on a roof, ”explains Mohite.

Recent iterations of perovskite solar technology have added 2D structures to improve stability. The Rice team decided to remove the “bulk” structure in 3D and go directly to 2D. It was then that the magic happened.

“We find that when you ignite the material, you squeeze it like a sponge and bring the layers together to improve load transport in that direction,” Mohite said.

“This effect gave us the opportunity to understand and adapt these fundamental light-matter interactions without creating complex heterostructures like stacked 2D transition metal dichalcogenides,” he added.

The actual amount of compression is tiny, but it makes a big difference. After exposure to a solar simulator, the team’s perovskite array contracted about 0.4% lengthwise and 1.0% vertically.

“It doesn’t sound like much, but this 1% contraction of the lattice spacing induces a great improvement in electron flow,” said co-lead author Wenbin Li, who is a graduate student of Rice Applied Physics. “Our research shows a threefold increase in the electronic conduction of the material. “

The trellis also quickly returned to its normal shape after the light was removed, indicating improved durability over 3D versions.

Group hug for American taxpayers

Coming back to this thing on a 10-year timeframe at 25% conversion efficiency from 60 years, this kind of accelerated R&D on clean tech will certainly come in handy now that the people of Earth only have one. window of about 10 years to prevent catastrophic climate change.

In the field of perovskite, part of the credit goes to the material itself. A leap forward in materials science over the past 30 years has also been taken into account, including the introduction of new, more powerful diagnostic tools funded by the taxpayer public, so pull us together as a group for us.

For example, Argonne National Laboratory physicist Joe Strzalka, who is co-author of the new solar cell study, credits the “ultra-clear” x-rays from the lab’s advanced photon source to have enabled for the team to observe nanoscale changes in the structure of their perovskites in real time.

“For changes like this, it’s important to do some operand studies,” adds Strzalka. “The same way your mechanic wants to run your engine to see what’s going on inside, we basically want to take a video of that transformation instead of a single snapshot.”

“The sensitive instruments of the APS 8-ID-E beamline allow ‘operando’ studies, that is, those carried out while the device is undergoing controlled changes in temperature or environment in normal operating conditions, ”adds Rice University.

APS was built in the 1990s, and apparently you haven’t seen anything yet.

“A full upgrade of the facility’s electron storage ring, which is scheduled to begin in April 2023, will increase the brightness of these X-rays up to 500 time and will allow new discoveries and innovations that we cannot yet imagine ”, enthuses Argonne. “New beamlines and improvements will further expand the capabilities of the APS, and keep it at the forefront of global x-ray science.

Accelerating climate action in the United States

The Rice team anticipates that the new and improved APS will help them take the next step on the R&D ladder.

“We are on the right track to achieve over 20% efficiency in designing cations and interfaces,” explains Sidhik. “That would change everything in the perovskite business, as people would then start using 2D perovskites for 2D perovskite / silicon and 2D / 3D perovskite tandems, which could lead to yields approaching 30%. “

It’s unfortunate that President Joe Biden’s Build Back Better climate action bill is kept in limbo, but the new perovskite research is just one of many initiatives that are bringing climate action into the picture. national policy, through the deep pockets of the Ministry of Defense.

In addition to the many cleantech initiatives undertaken by the military and navy, the U.S. Air Force is also pushing the cleantech envelope into new territories.

Follow me on Twitter @TinaMCasey.

Photo: “Rice University graduate student Wenbin Li prepares 2D perovskite solar cell for testing in a solar simulator” (Credit: Jeff Fitlow / Rice University).

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