Researchers at Georgia Institute of Technology and Purdue University have developed new solar cells based on natural substances derived from plants, including trees. The organic solar cells have an efficiency of 2.7 percent – a new high for cells on substrates derived from renewable raw materials – and can be easily recycled.
The research was led by Georgia Tech College of Engineering Professor Bernard Kippelen, who expects to help make sustainable and renewable solar cell technology truly practicable for the first time.
“The development and performance of organic substrates in solar technology continues to improve, providing engineers with a good indication of future applications,” explained Kippelen. “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 its lifecycle.”
Organic solar cells are typically fabricated on glass or plastic, neither of which is easy to recycle. However, Kippelen's solar cells are fabricated on cellulose nanocrystal (CNC), which is derived from plants, including trees.
To recycle the new cells at the end of their lifecycle, they're simply immersed in water at room temperature. Within minutes of soaking, the CNC substrate dissolves, leaving the solar cell to be easily separated into its major components.
The CNC substrates are optically transparent, enabling light to pass through before being absorbed by a very thin layer of an organic semiconductor. Though 2.7 percent efficiency is relatively inefficient compared to, say, the recent strides in solar cell technology made by Empa, the environmental benefits of producing easily recyclable solar cells are clear.
In addition, the researchers expect to improve the efficiency of the new solar cells yet further in the future.
“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 research was published in the journal Scientific Reports.
Source: Georgia Tech
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