According to researchers at the Chemistry and Nanoscience Center at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), there is a cost-effective alternative to gold or silver for enhancing the efficiency of perovskite solar cells, making it more affordable to commercialize this promising technology.
Kai Zhu, a senior scientist at NREL along with his colleagues from Northern Illinois University have developed a cost-effective alternative to precious metals for enhancing the efficacy of these cells. Their solution is simple — a nickel-doped graphite layer combined with a bismuth-indium alloy layer. These two layers can be integrated into the perovskite device by simply painting them on, which is a low-cost fabrication method.
The research received financial support from multiple organizations, including the Department of Energy’s Solar Energy Technologies Office and the National Science Foundation. The detailed findings have been published in the journal ACS Energy Letters, in a new paper titled “Nickel-Doped Graphite and Fusible Alloy Bilayer Back Electrode for Vacuum-Free Perovskite Solar Cells.”
Zhu said, “A layer of gold in a solar panel or even a layer of silver is probably too expensive. It would make the solar panel not affordable for most people.”
Tao Xu, a chemistry professor at Northern Illinois University and Zhu’s co-author of the new paper, said, “Our team has identified a potentially disruptive technology that could help reduce the infrastructure investment for the use of highly promising perovskite solar cells in solar panels. Our approach replaces costly gold, commonly used to make the back-metal electrode in these solar cells through an expensive high-temperature vacuum-chamber process. Instead of gold, we use inexpensive materials that can be readily laminated to thin films at atmospheric pressure and mild temperatures. We think this will be an appealing low-cost solution that could help speed the commercialization of perovskite solar cells.”
Previously, Xu and Zhu have collaborated on ways safely isolate lead in the event of damage to perovskite solar cells, given the presence of trace amounts of the element. The research team includes co-authors So Yeon Park from NREL, as well as researchers from Northwestern University and Argonne National Laboratory in Illinois.
Zhu also noted that the utilization of the new materials in the perovskite solar cell resulted in a laboratory efficiency of 21%. With additional research and development, one can expect the efficiency to go up further, potentially reaching levels closer to the record efficiency of 26% achieved by perovskite solar cells using precious metals. Compared to carbon, metals exhibit superior electrical conductivity.
Perovskite solar cells are manufactured by applying chemical compounds onto a substrate. Each layer in the cell has a specific function and the perovskite layer functions as the semiconductor. When photons from sunlight interact with the cell, they force the electron to move in one direction, generating a vacancy or “hole” that moves in the opposite direction. But to initiate this movement, an appropriate energy level is required, which results in the generation of an electric current. Both the graphite material and gold possess the necessary energy level for initiating movement.
The researchers have identified that by removing the layer of precious metals, the manufacturing cost of perovskite solar cells can be substantially reduced. As per their analysis, in a perovskite-based solar plant with a gigawatt of power output, implementing the graphite/alloy bilayer for the contact electrodes could result in cost reductions ranging from 4 to 1,000 times, depending on materials used for the other components. “That’s the selling point for this approach,” Zhu said.
