Researchers Create Transparent, Flexible Solar Cells

October 8, 2008

Imagine solar cells that can be worn on your body, or transparent solar panels that can be placed on a window.

Recent research performed by Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern University's McCormick School of Engineering, and his colleagues from the University of Illinois-Urbana Champaign could make that a reality. Their research was recently published as the cover article of Nature Materials. Nature also published a commentary "Solar cells go around the bend" in its News & Views.

The group has developed a new process of creating very thin solar cells that can be combined in flexible and transparent arrays. In order to make the solar cells, researchers carved tiny microcell arrays from a block of silicon, then etched the outlines of the microcells onto the surface of the silicon. The surface is then “doped” with boron and phosphorous to make electronic junctions and contacts. Then, to make large-scale bendable solar cells, the researchers used a printing technique and pressed a flat rubber stamp onto the arrays of microcells. The microcells stick to the surface of the stamp and are transferred onto a flexible substrate when the stamp is pressed onto the flexible substrate. Researchers then construct electrodes to connect the microcells to each other.

“The conventional silicon solar cells are large and bulky, usually sitting on the rooftop. Their low efficiency and high cost due to the need for high-quality silicon limit their use. The new silicon solar cells use only one tenth of amount, and are lightweight and flexible,” Huang says.

By controlling the spacing of the microcells, researchers can make the arrays virtually transparent. They can also make them anywhere between 10 and 90 percent transparent.

“That means the new silicon solar cells can be applied to many places such as fabrics, windows of buildings, and automobiles,” Huang says.

The arrays are also considerably light, which makes them transported and installed more easily than existing solar cells. And because they work just as efficiently when bent as when flat, they can be fixed to curved surfaces, like your body.

The research has already received coverage from Reuters and the New York Times.

Read the paper