solar success

Houston research team develops breakthrough process for light-harvesting crystals in DOE-backed project

Rice University engineers and collaborators developed a technology that converts light into electricity. Photo by Jeff Fitlow/Rice University

A team of Rice researchers have developed a breakthrough synthesis process for developing light-harvesting materials that can be used in solar cells to convert light into electricity.

Detailed in an October study in Nature Synthesis, the new process is able to more closely control the temperature and time of the crystallization process to create 2D halide perovskites with semiconductor layers of “ideal thickness and purity,” according to a release from Rice.

The process, known as kinetically controlled space confinement, was developed by Rice University chemical and biomolecular engineer Aditya Mohite, along with others at Northwestern University, the University of Pennsylvania and the University of Rennes. The research was backed by the Department of Energy, the Army Research Office, the National Science Foundation and a number of other organizations.

“This research breakthrough is critical for the synthesis of 2D perovskites, which hold the key to achieving commercially relevant stability for solar cells and for many other optoelectronic device applications and fundamental light matter interactions,” Mohite said in a statement.

Traditional synthesis methods for creating 2D halide perovskites, which have been shown to offer a high-performance low-cost way to produce solar cells, have generated uneven crystal growth when attempting to reach a higher n value. And uneven crystal growth can result in a less reliable material, while a high n value can result in higher electrical conductivity, among other benefits.

The study shows how the kinetically controlled space confinement method can gradually increase n values in 2D halide perovskites, which will assist in the production of crystals with a certain thickness.

“We designed a way to slow down the crystallization and tune each kinetics parameter gradually to hit the sweet spot for phase-pure synthesis,” Jin Hou, a Ph.D. student at Rice and a lead author on a study, said in a statement.

The process is expected to improve the stability and lower the costs of emerging technologies in optoelectronics, or the study and application of light-emitting or light-detecting devices, and photovoltaics, the conversion of thermal energy into electricity.

"This work pushes the boundaries of higher quantum well 2D perovskites synthesis, making them a viable and stable option for a variety of applications,” Hou added.

Houston universities have been making major strides relating to crystallization processes in recent months.

In September, the University of Houston announced The Welch Foundation awarded its inaugural $5 million Catalyst for Discovery Program Grant to establish the Welch Center for Advanced Bioactive Materials Crystallization. The center will build upon UH professor Jeffrey Rimer's work relating to the use of crystals to help treat malaria and kidney stones.

Over the summer, a team of researchers at UH also published a paper detailing their discovery of how to use molecular crystals to capture large quantities of iodine, one of the most common products of radioactive fission, which is used to create nuclear energy.

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Rice University scientists' “recharge-to-recycle” reactor has major implications for the electric vehicle sector. Photo courtesy Jorge Vidal/Rice University.

Engineers at Rice University have developed a cleaner, innovative process to turn end-of-life lithium-ion battery waste into new lithium feedstock.

The findings, recently published in the journal Joule, demonstrate how the team’s new “recharge-to-recycle” reactor recharges the battery’s waste cathode materials to coax out lithium ions into water. The team was then able to form high-purity lithium hydroxide, which was clean enough to feed directly back into battery manufacturing.

The study has major implications for the electric vehicle sector, which significantly contributes to the waste stream from end-of-life battery packs. Additionally, lithium tends to be expensive to mine and refine, and current recycling methods are energy- and chemical-intensive.

“Directly producing high-purity lithium hydroxide shortens the path back into new batteries,” Haotian Wang, associate professor of chemical and biomolecular engineering, co-corresponding author of the study and co-founder of Solidec, said in a news release. “That means fewer processing steps, lower waste and a more resilient supply chain.”

Sibani Lisa Biswal, chair of Rice’s Department of Chemical and Biomolecular Engineering and the William M. McCardell Professor in Chemical Engineering, also served as co-corresponding author on the study.

“We asked a basic question: If charging a battery pulls lithium out of a cathode, why not use that same reaction to recycle?” Biswal added in the release. “By pairing that chemistry with a compact electrochemical reactor, we can separate lithium cleanly and produce the exact salt manufacturers want.”

The new process also showed scalability, according to Rice. The engineers scaled the device to 20 square centimeters, then ran a 1,000-hour stability test and processed 57 grams of industrial black mass supplied by industry partner Houston-based TotalEnergies. The results produced lithium hydroxide that was more than 99 percent pure. It also maintained an average lithium recovery rate of nearly 90 percent over the 1,000-hour test, showing its durability. The process also worked across multiple battery chemistries, including lithium iron phosphate, lithium manganese oxide and nickel-manganese-cobalt variants.

Looking ahead, the team plans to scale the process and consider ways it can sustain high efficiency for greater lithium hydroxide concentrations.

“We’ve made lithium extraction cleaner and simpler,” Biswal added in the release. “Now we see the next bottleneck clearly. Tackle concentration, and you unlock even better sustainability.

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