Progress Made in Plastic Solar-Cell Technology

Scientists at the University of Washington, led by Associate Professor of Chemistry David Ginger, have recently taken another step forward towards completing the scientific objective of producing cheap, plastic-based solar cells able to transform more than ten percent of the sunlight they absorb into electricity. One of the major obstacles research groups around the world have met until now in doing this has consisted in unsuccessful attempts at creating a stable structure at the nanoscale, made up of carbon-based materials.

“The solution to the energy problem is going to be a mix, but in the long term solar power is going to be the biggest part of that mix,” Ginger says. In a new, innovative process, the UW team has managed to devise a way of constructing tiny bubbles and channels inside nanoscale plastic structures. The channels are roughly 1/10,000th the size of a human hair. What is more amazing is the fact that the structures are not imprinted or engraved into the finished plastic product, but built-in, as a byproduct of a high-temperature production process known as annealing.

The most common way to make solar cells at this point is for researchers to blend two types of materials into a thin film, and then subject them to annealing, so as to increase their performances. The amount of heat applied and the duration of the cooking process is used to determine the number of bubbles and channels inside the mix, and thus these traits can be easily controlled. What's difficult to understand is the exact nature of the relationships between baking time, bubble size, channel connectivity and efficiency, which essentially gives the overall performance of the plastic solar cell.

Ginger reveals that one of the most useful lab tools in future solar-cell research will be the atomic force microscope. He and his team have managed to use such a device to analyze the size, disposition and connectivity of channels inside plastic solar cells made from polythiophene and fullerene. The mix has not yet achieved a ten-percent absorption efficiency, but the observation tool could allow this team or another one to come to the correct mix in the future.