Current solar panels need two materials to work: one that absorbs light and excites electrons, and another that gets those electrons to flow in one direction, producing electrical current.
Single materials that can do both of these jobs have been known for decades, but they have only been shown to work with ultraviolet (UV) light. This UV light is highly energetic—powerful enough to cause cancers by damaging the DNA in skin cells—but is only a fraction of the light produced by the sun. Having a material that could both capture photons from the sun’s bountiful visible light and get current to flow would open the door for an entirely new way of making solar panels.
Researchers at Penn and Drexel have done just that, using computer modeling to devise such a material, then fabricating and testing it in the lab.
The study was led by professor Andrew M. Rappe and research specialist Ilya Grinberg of the Department of Chemistry in Penn’s School of Arts & Sciences, along with chair Peter K. Davies of the Department of Materials Science and Engineering in the School of Engineering and Applied Science, and professor Jonathan E. Spanier of Drexel’s Department of Materials Science and Engineering.
This material could facilitate solar panels that would have several advantages over existing ones. Not only would they be simpler to manufacture, they would be inherently more efficient than their two-material counterparts, as some of sunlight’s energy is lost as electrons wait to make the jump from one material to the other.
The researchers began their search for the new material by theorizing composites of existing ones based on the two qualities they needed to combine.
“We know a family of materials that can [give electrons a direction in which to flow], and we know a family of materials that can absorb visible light,” Rappe says. “The challenge was to find compatibility between those two properties.”
After several failed attempts to physically produce the specific materials they had theorized, the researchers had success with a combination of potassium niobate and barium nickel niobate. The resulting material is what is known as a “perovskite crystal,” a structure commonly found in nature in composites made of two metals and oxygen. The researchers made their breakthrough fine-tuning the ratio of these metal atoms in the final product.
Future research will go toward improving the material’s efficiency and scaling it up to sizes useful for making solar panels.