Energy futuresResearchers develop record-breaking plastic solar cell

Researchers at the University of California, Los Angeles (UCLA) have made a breakthrough with plastic solar cells, creating a record-breaking polymer cell that converts 10.6 percent of the sun’s energy into electricity.

Currently silicon solar cells are more efficient, but polymer solar cells are cheaper, more flexible, and lighter, which is why UCLA professor Yang Yang and his team are actively working to boost polymer solar cell performance.

Last July, Yang Yang, a professor of materials science and Engineering, set the previous polymer record at 8.6 percent. Yang hopes that eventually his team will be able to fine tune the polymer cells, based on a photovoltaic polymer developed by Sumitomo Chemical, a Japanese firm, to compete with existing silicon cells.

The latest plastic solar cells use two layers to capture the different bands of light.

“The solar spectrum is very broad, from the near infrared through the infrared to the ultraviolet, and one single solar-cell component can’t do it all,” Yang explained to MIT’s Technology Review.

In addition to their inexpensive nature, plastic polymer solar cells can be manufactured relatively easily in a process similar to printing ink on a paper.

The organic material can be made from a solution that is printed on to paper in layers, but Alan Heeger, the co-winner of the 2000 Nobel Prize for his discovery of conductive polymers, explains that the process is both relatively simple and quite complex.

“There are no high temperatures involved, and manufacturing is simple,” Heeger said, but determining the proper mix for each layer in a cell without it bleeding through to the layer below is quite difficult.

In addition with each additional layer, the complex becomes increasingly more challenging. Furthermore matching the electrical properties of each layer and connecting them is tricky.  

According to MIT’s Technology Review, Yang hopes to eventually create a polymer cell with an efficiency of 15 percent, as a cell’s performance usually drops by a third when taken out of a laboratory setting.

With a 15 percent efficient polymer cell, Yang believes, these new cells will be able to compete with existing thin-film silicon based solar cells.