With a view to one day developing transparent solar cells that can double as windows in homes and other buildings, an international team of scientists has demonstrated a new type of transparent electrode that can function as a key building block. The breakthrough overcomes some performance issues with previous efforts in this area, and lays the groundwork for advanced tandem solar cells that combine the strengths of two separate but complimentary technologies.

Silicon-based solar cells have been a mainstay of solar technology for decades, but lately we're seeing perovskite-based cells make their mark. Ever-improving efficiencies have placed these solar cells front and center in conversations about renewable energy, and one exciting possibility includes combining them with traditional silicon-based cells to lower the cost and offer greater conversion efficiencies.

Tandem solar cells are the focus of this latest research, which actually builds on earlier work around electrode materials for perovskite solar cells. Scientists had shown how ultrathin films of gold could be used as transparent electrodes for these cells, but had struggled to create a uniform layer, which led to poor conductivity. The authors of the new study have now found that using chromium as a seed layer for the gold film to form on sidesteps these issues.

“Normally, if you grow a thin layer of something like gold, the nanoparticles will couple together and gather like small islands,” says Dong Yang, assistant research professor of materials science and engineering at Penn State. “Chromium has a large surface energy that provides a good place for the gold to grow on top of, and it actually allows the gold to form a continuous thin film.”