A discovery by a team of researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) and Northern Illinois University has developed a layer made of nickel-doped graphite combined with a bismuth-indium alloy as a cost-effective alternative to the gold layer used on perovskite solar cells.

The two layers can be easily integrated into the perovskite device by simply painting them on, making the fabrication process cost-effective and accessible and perovskite solar cells commercially viable.

Traditionally, perovskite solar cells have relied on a thin layer of gold or silver as a back-metal electrode, but the high cost of these materials has limited their widespread adoption.

Recognizing this challenge, Dr. Kai Zhu, a senior scientist at NREL, and his colleague, Professor Tao Xu from Northern Illinois University, set out to find a more affordable solution.

The research findings, published in the journal ACS Energy Letters, highlight the potential of the nickel-doped graphite and fusible alloy bilayer back electrode for vacuum-free perovskite solar cells.

The study describes how the novel approach could significantly reduce the infrastructure investment required to deploy perovskite solar cells in solar panels.

Professor Tao Xu explains, “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 up the commercialization of perovskite solar cells.”

Dr. Zhu adds, “Our team has identified a potentially disruptive technology that could help reduce the cost of highly promising perovskite solar cells in solar panels. By replacing the expensive layer of gold with affordable materials, we can make perovskite solar panels more accessible and affordable for the general population.”

The new materials developed by Xu and Zhu demonstrate promising results, with laboratory efficiency reaching 21%.

The researchers anticipate that further advancements will enhance the efficiency, bringing it closer to perovskite solar cells made with precious metals, which currently hold a record efficiency of 26%.

Cost analyses indicate that implementing the graphite/alloy bilayer for contact electrodes in a gigawatt-scale perovskite-based solar project can lead to cost reductions ranging from four to one thousand times, depending on the other materials used for back layers.

Dr. Zhu concludes, “That’s the selling point for this approach. It has the potential to revolutionize the cost structure of perovskite solar cells and pave the way for their widespread commercialization.”

The research was partly supported by the Department of Energy’s Solar Energy Technologies Office and the National Science Foundation.

Last December, researchers from the Fraunhofer Institute of Solar Energy Systems (ISE) collaborated with industry partners to achieve an efficiency of 22.55% in a perovskite-silicon tandem solar cell measuring over 100 square centimeters.

Earlier in the month, scientists at the Swiss Laboratories for Material Science & Technology, Empa, claimed to have developed a low-temperature method using silver to produce a bifacial perovskite-copper indium gallium selenide tandem solar cell.