Organic solar cells would create renewable energy, rely less on fossil fuels, be recyclable, and be cheaper than current cells.
Considering that green plants have been converting sunlight into sugar for millions of years, it’s only natural that scientists would look to them as a model for improving solar energy technology. Scientists recently developed an organic substitute that processes sunlight as a plant does. Advancing this technology could aid the evolution of solar power as a sustainable energy strategy.
Most traditional solar cells are made of glass or plastic, which makes them breakable and hard to recycle. In order to address these problems, researchers at the Georgia Tech College of Engineering experimented with organic compounds made from wood. The compounds, dubbed cellulose nanomaterials (CNs), are very thin and come from trees (a renewable resource).
CNs — a fancy way of saying “miniscule plant parts” — achieve reasonable solar efficiency and lend themselves to cheap production on a mass scale. Laboratory tests also suggest that simple solvents can break down CNs into their constituent components, allowing old, spent solar cells to make a simple and inexpensive transition into new ones.
“Organic solar cells must be recyclable,” Bernard Kippelen, a Georgia Tech professor and research team lead, said in a statement. “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.”
While CNs solve the problem of sustainability neatly, efficiency is still a major issue. Kippelen writes in a research paper that less recyclable organic solar cells have achieved efficiencies as high as 10.6 percent (i.e., the cell can effectively process 10.6 percent of the energy absorbed from sunlight). In order to be useful in a domestic or industrial setting, a solar cell needs an efficiency of at least 5 percent.
Currently, Kippelen’s organic cells are 2.7 percent efficient. Because the study focused on eco-friendliness rather than on efficiency, however, the low efficiency rating is not necessarily a huge setback for the project.
“Our next steps will be to work toward improving the power-conversion efficiency [to] over 10 percent, levels similar to [those seen for] cells fabricated on glass or petroleum-based substrates,” Kippelen said.
If cheap, efficient renewable solar cells sound too good to be true, bear in mind that the technology is still being developed and is still years away from being commercialized.