Encouraging results demonstrate an effective approach to mitigating lead leakage
Yongtao Liu

Image: Solar cells converts sunlight to electricity


The Sun is our closest star providing us light and warmth. However, it was only after 1954 that solar energy began to be an attainable electricity source because of the first silicon solar cell developed by Bell Labs. A solar cell is a semiconductor device that can directly convert the light energy to electricity through the photovoltaic effect. After about 70 years of development, solar cells are one of the most promising clean energy technologies to address increasing global energy demands and meet the goal of sustainable development.

Over the last decade perovskite solar cells have exhibited a remarkable increase in conversion efficiency from about 3% to above 25%, which positioned the perovskite solar cell as a promising candidate in solar energy technologies. However, even with high efficiency, low cost, and easy fabrication, barriers to commercializing perovskite solar cell remain. Most highly efficient perovskite solar cells are made with lead-containing perovskite compounds, which can leach out of the solar cells if damaged. Unfortunately, lead is a toxic heavy element that can cause severe harm to living organisms through environmental contamination. Therefore, minimizing or even eliminating lead leakage is a critical step before perovskite solar cells can be adopted as a widespread commercial technology.

In recent years, extensive efforts have been undertaken to improve the stability of perovskite materials to mitigate their decomposition and lead leakage. A research team financially supported by the Hybrid Organic-Inorganic Semiconductors for Energy (CHOISE) Energy Frontier Research Center (EFRC) recently developed a method for preventing lead leakage from degraded and decomposed perovskite solar cells to reduce lead release to the environment.[1] The team, composed of scientists from the University of North Carolina at Chapel Hill and Duke University, applied a lead-absorbing layer based on a low-cost and chemically robust cation-exchange resin (CER) to prevent lead leakage from damaged perovskite solar cells. The commercialized hydrogen form of this CER (Amberlyst 15) was converted to the sodium form by mixing with an aqueous NaOH solution before applying to perovskite solar cells.

To understand the how this CER layer absorbs lead, the team performed computational analysis, which revealed that this layer has high binding energy with lead ions. As such, it exhibits high adsorption capacity and high adsorption rate of lead ions. Then, the team further performed absorption performance tests to confirm the CER layer’s functionality of preventing lead leakage. In absorption performance tests, the CER layer was first coated on perovskite photovoltaic devices. Afterward, the photovoltaic devices were intentionally broken with ice balls, and then had either water droplets fall on the device or were placed in water to simulate real operations under severe weather conditions such as hail, rain, and flooding. Inspiringly, CER-layer-protected photovoltaic devices exhibited very small lead leakage compared to the reference devices without the CER layer, demonstrating the effective performance of the CER layer on preventing lead leakage. Moreover, incorporating CER into carbon-based electrodes in perovskite solar cells reduces lead leakage without compromising the performance of solar cells. Remarkably, the CER incorporated solar cells exhibit very low lead leakage, with leakage levels below what is considered safe for drinking water.

These encouraging results demonstrate an effective approach to mitigating lead leakage from perovskite photovoltaic modules, which is a vital step for commercializing this new technology. This research highlights that scientists are working to develop safe and reliable technologies for our society’s biggest energy challenges for a bright and safe future for all of us.

More Information

1. Chen, S. et al. Trapping lead in perovskite solar modules with abundant and low-cost cation-exchange resins. Nature Energy 5, 1003-1011 (2020).


Acknowledgment from reference: This research was financially supported mainly by the University of North Carolina Chapel Hill. We acknowledge support for the first-principles computations by the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center (EFRC) funded by the US Department of Energy, Office of Basic Energy Sciences, Office of Science. We used the BET surface area and pore diameter analyser (Quantachrome NOVA 2000e) at the AMPED EFRC Instrumentation Facility established by the Alliance for Molecular PhotoElectrode Design for Solar Fuels, an EFRC funded by the US Department of Energy, Office of Basic Energy Sciences, Office of Science, under award number DE-SC0001011).

About the author(s):

Yongtao Liu is a postdoc in Center for Nanophase Materials Science at Oak Ridge National Laboratory and a member of the EFRC Center for 3D Ferroelectric Microelectronics. His research focuses on machine learning-driven autonomous scanning probe microscopy for materials discoveries. ORCID ID # 0000-0003-0152-1783.

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