Georgia Institute of Technology and Purdue University
researchers have developed efficient solar cells using natural substrates
derived from plants such as trees. Just as importantly, by fabricating them on
cellulose nanocrystal (CNC) substrates, the solar cells can be quickly recycled
in water at the end of their lifecycle.
The technology is published in the journal Scientific Reports, the latest
open-access journal from the Nature Publishing Group.
How it will work
The researchers report that the organic solar cells reach a
power conversion efficiency of 2.7 percent, an unprecedented figure for cells
on substrates derived from renewable raw materials. The CNC substrates on which
the solar cells are fabricated are optically transparent, enabling light to
pass through them before being absorbed by a very thin layer of an organic
During the recycling process, the solar cells are simply
immersed in water at room temperature. Within only minutes, the CNC substrate
dissolves and the solar cell can be separated easily into its major components.
Georgia Tech College of Engineering Professor Bernard
Kippelen led the study and says his team’s project opens the door for a truly
recyclable, sustainable and renewable solar cell technology.
“The development and performance of organic substrates in
solar technology continues to improve, providing engineers with a good
indication of future applications,” said Kippelen, who is also the director of
Georgia Tech’s Center for Organic Photonics and Electronics (COPE). “But
organic solar cells must be recyclable. Otherwise we are simply solving one
problem, less dependence on fossil fuels, while creating another, a technology
that produces energy from renewable sources but is not disposable at the end of
Previously on plastic
To date, organic solar cells have been typically fabricated
on glass or plastic. Neither is easily recyclable, and petroleum-based
substrates are not very eco-friendly. For instance, if cells fabricated on
glass were to break during manufacturing or installation, the useless materials
would be difficult to dispose of. Paper substrates are better for the
environment, but have shown limited performance because of high surface
roughness or porosity. However, cellulose nanomaterials made from wood are
green, renewable and sustainable. The substrates have a low surface roughness
of only about two nanometers.
“Our next steps will be to work toward improving the power
conversion efficiency over 10 percent, levels similar to solar cells fabricated
on glass or petroleum-based substrates,” said Kippelen. The group plans to
achieve this by optimizing the optical properties of the solar cell’s
Purdue School of Materials Engineering associate professor
Jeffrey Youngblood collaborated with Kippelen on the research.
A provisional patent on the technology has been filed with
the US Patent Office.
There’s also another positive impact of using natural
products to create cellulose nanomaterials. The nation’s forest product
industry projects that tens of millions of tons of them could be produced once
large-scale production begins, potentially in the next five years.
The research is the latest project by COPE, which studies
the use and development of printed electronics. Last year the centre created
the first-ever completely plastic solar cell.