Student researchers evaluate environmental effects of new solar cells

Solar energy is better for the environment than burning fossil fuels, but most of the photovoltaic cells that collect and convert the sun's rays into electricity contain toxic elements like lead, and that can be dangerous if they leak into the ground.

From left, Associate Professor Tara P. Dhakal, PhD students Wendifer Reyes Ramos and Tasneem Tawalbeh, and Assistant Professor Yuxin Wang at the NYSP2I Student and Faculty Program Symposium at Rensselaer Polytechnic Institute. Image Credit: Provided.

New low-cost perovskite solar cells have about three times less lead than traditional silicon solar technology, which uses lead in its metal contacts.

This summer, students in the New York State Pollution Prevention Institute (NYSP2I) Student and Faculty Research Program at Binghamton University investigated a better way to make the perovskite solar cells by replacing the lead with a safer alternative - tin - to further reduce the potentially hazardous effects on groundwater and soil during deployment of solar cells and at the end of their life.

The annual summer-long program enables students to propose, develop, design and research solutions to real-world environmental challenges. This year's projects focused on green chemistry and safer chemicals.

"The idea is to reduce lead's percentage in perovskite solar panels by suggesting other metals or elements," said Tasneem Tawalbeh, a PhD student at the Thomas J. Watson College of Engineering and Applied Science's School of Systems Science and Industrial Engineering. "The best alternative was tin, but we cannot produce or use tin-based solar cells because it's not stable. Instead, a mix of tin and lead provides both stability and safety in addition to high efficiency."

Working under the supervision of SSIE Assistant Professor Yuxin Wang and Associate Professor Tara P. Dhakal from Watson College's Department of Electrical and Computer Engineering, the students worked on a design for low-lead perovskite solar cells that would significantly cut greenhouse gas emissions during manufacturing, deployment and operation.

The team also sought to further reduce the lead content in perovskite solar cells by at least 50 percent and conducted environmental toxicity studies through degradation testing to assess chemical leaching.

Clara Brenton, from Vestal, is a junior this fall at SUNY College of Environmental Science and Forestry. Her major is paper engineering, but she joined the program to get real-world lab experience.

"This kind of research is pretty far outside of what I usually do, but it's interesting," she said.

Sam Gold '24, who earned his bachelor's degree in environmental studies and political science, is pursuing a master's degree in industrial and systems engineering through the 4+1 program starting this fall. His part of the project was setting up the lead-leaching experiments and measuring whether the results fell into standards set by the U.S. Environmental Protection Agency.

"I learned that green energy still has environmental impacts," Gold said. "I feel like most people don't really think about that, because they think the sun is basically free energy, but there are still effects from the technology used to capture that energy."

Wendifer Reyes Ramos, a PhD student in materials science and engineering who works with Dhakal, sees the research as an important step to better clean energy methods.

"For future large-scale application of perovskite solar cells, it is good to know what the effects of lead leaching would be and how we can prevent that," she said.

Dhakal said he is proud of what the students accomplished this summer: "While our investigation toward further reducing the lead content in the perovskite solar cells will continue, the NYSP2I project achieved a significant milestone in terms of mitigating the lead leaching into the environment through the development of efficient encapsulation method, which was only possible due to our students' diligent effort over the summer."

Tawalbeh and Reyes Ramos presented their findings during the NYSP2I Student and Faculty Program Symposium on Sept. 20 at Rensselaer Polytechnic Institute (RPI) in Troy, N.Y. The PhD students displayed a poster for attendees and made a 20-minute presentation about the project.

"This interdisciplinary project benefits our undergraduate and graduate students in many ways, including developing critical thinking skills about different topics and developing transferable skills that can be applied to future learning experiences," Wang said.

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