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Houston lab's breakthrough light-harvesting processes near market readiness

The new process developed by Rice University researchers makes solar cells that are about 10 times more durable than traditional methods. Photos by Jeff Fitlow/Rice University

A groundbreaking Rice University lab has made further strides in its work to make harvesting light energy more efficient and stable.

Presented on the cover of a June issue of Science, a study from Rice engineer Aditya Mohite's lab uncovered a method to synthesize a high-efficiency perovskite solar cell, known as formamidinium lead iodide (FAPbI3), converting them into ultrastable high-quality photovoltaic films, according to a statement from Rice. Photovoltaic films convert sunlight into electricity.

The new process makes solar cells that are about 10 times more durable than traditional methods.

“Right now, we think that this is state of the art in terms of stability,” Mohite said in a statement. “Perovskite solar cells have the potential to revolutionize energy production, but achieving long-duration stability has been a significant challenge.”

The change come from "seasoning" the FAPbI3 with 2D halide perovskites crystals, which the Mohite lab also developed a breakthrough synthesis process for last year

The 2D perovskites helped make the FAPbI3 films more stable. The study showed that films with 2D perovskites deteriorated after two days of generating electricity, while those with 2D perovskites had not started to degrade after 20 days.

“FAPbI3 films templated with 2D crystals were higher quality, showing less internal disorder and exhibiting a stronger response to illumination, which translated as higher efficiency," Isaac Metcalf, a Rice materials science and nanoengineering graduate student and a lead author on the study, said in the statement.

Additionally, researchers say their findings could make developing light-harvesting technologies cheaper, and can also allow light-harvesting panels to be lighter weight and more flexible.

"Perovskites are soluble in solution, so you can take an ink of a perovskite precursor and spread it across a piece of glass, then heat it up and you have the absorber layer for a solar cell,” Metcalf said. “Since you don’t need very high temperatures ⎯ perovskite films can be processed at temperatures below 150 Celsius (302 Fahrenheit) ⎯ in theory that also means perovskite solar panels can be made on plastic or even flexible substrates, which could further reduce costs.”

Mohite adds this has major implications for the energy transition at large.

“If solar electricity doesn’t happen, none of the other processes that rely on green electrons from the grid, such as thermochemical or electrochemical processes for chemical manufacturing, will happen,” Mohite said. “Photovoltaics are absolutely critical.”

The Mohite lab's process for creating 2D perovskites of the ideal thickness and purity was published in Nature Synthesis last fall. At the time, Mohite said the crystals "hold the key to achieving commercially relevant stability for solar cells."

About a year ago, the lab also published its work on developing a scalable photoelectrochemical cell. The research broke records for its solar-to-hydrogen conversion efficiency rate.

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A View From HETI

The world is trending toward producing 82 million metric tons of flame-retardant plastic waste by 2030. Photo via Unsplash

Researchers at Rice University have developed a new technique to efficiently recycle electronic waste and harvest critical minerals using rapid heating.

Most electronic devices use flame-retardant plastic. The plastic is formulated from a critical metal called antimony.

However, recapturing antimony is typically a challenging task since it first has to be released from the plastic. As it is released, other compounds can form, such as organic bromides, which are toxic and difficult to capture. However, the organic bromides can also be reused and have applications in industrial chemicals when safely captured.

“Conventionally heating the plastic releases the antimony in a volatile and difficult-to-collect form as well as creating and releasing hazardous organic bromide compounds,” Leo Haoxin Ye, first author of the paper and a graduate student at Rice, said in a news release. “Other options are risky or more impractical, such as using strong acids, organic solvents or multistep treatment options.”

To address this issue, leading Rice chemistry professor James Tour, Ye and their team adapted Tour’s flash Joule heating technique, which heats materials to hundreds of degrees Celsius in milliseconds, according to Rice.

The team ground up flame-retardant plastic waste and placed it between two sheets of electrically heated carbon paper before using what’s known as isothermal-clamped flash Joule heating to release and collect the antimony.

The team found that limiting the time the plastic spent in the high temperature range dramatically reduced the production of the hazardous organic bromide compounds. The plastic remained between 200 degrees and 500 degrees Celsius for only 9.4 milliseconds, according to Rice.

Through the process, the team recovered 90 percent of antimony from tested materials and converted 83 percent of the bromide into hydrogen bromide. Their findings were published this month in the journal Nature Chemical Engineering.

“Isothermal-clamped flash Joule heating could improve the speed, safety and practicality of antimony recovery from discarded flame-retardant plastics,” Tour added in the release. “This represents an important step forward to conserving and reusing our critical antimony supply while also regenerating bromide salts for reuse.”

The study noted that the world is currently trending toward producing 82 million metric tons of flame-retardant plastic waste by 2030, which adds to the fact that e-waste is the fastest-growing solid waste stream in the world.

The research was funded by the Air Force Office of Scientific Research and the U.S. Army Corps of Engineers.

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