Researchers at the University of Cambridge claimed to have found a way to prevent the loss of electric current that declines the efficiency of organic solar cells.

Organic solar cells are flexible, semi-transparent, cheap, and environmentally friendly to produce. These cells can expand the range of applications for solar technology and could be wrapped around the exteriors of buildings. The cells could also be used for the efficient recycling of the energy used for indoor lighting.

The researchers said a loss pathway in organic solar cells makes them less efficient than silicon solar cells at converting sunlight into power. They found that a critical loss mechanism in an organic solar cell is caused by recombination to triplet exciton.

Electrons in solar can be lost through recombination, where electrons lose their energy and fall back into an empty hole state. Organic solar cells are more prone to recombination due to stronger attraction between the electron and hole in carbon-based materials than in silicon. Therefore, it requires electron donor material and an electron acceptor material to stop the electron and hole from rapid recombination.

To prevent the recombination of electrons and holes into triplet excitons, the researchers used a combination of spectroscopy and computer modeling. They engineered strong molecular interactions between the electron donor and electron acceptor materials. They also manipulated molecules inside an organic solar cell to prevent the loss of electric current through triplet excitons.

Alexander Gillett, the lead author from the University of Cambridge’s Cavendish Laboratory, said, “Organic solar cells can do lots of things that inorganic solar cells cannot, but their commercial development has plateaued in recent years, in part due to their inferior efficiency. A typical silicon-based solar cell can reach efficiencies as high as 20% to 25%, while organic solar cells can reach efficiencies of around 19% under laboratory conditions, and real-world efficiencies of about 10% to 12%.”

According to the researchers, this method provides a strategy to achieve organic solar cells with efficiencies of over 20% by stopping recombination into triple exciton states. They also offer design rules for electron donor and electron acceptor materials to achieve an efficiency of over 20%. The guidelines will enable chemistry groups to design new material that blocks recombination into triplet excitons and enhance organic solar cells with efficiency closer to silicon solar cells.

Last year, a research team from the South China University of Technology developed a new method of producing organic solar cells, eliminating the need for potentially toxic materials while maintaining high conversion efficiencies.

Mercom had earlier reported that a research team from the University of Michigan set a new efficiency record for color-neutral, transparent solar cells, with 8.1% efficiency and 43% transparency through an organic/carbon-based design.

Image credit: University of Cambridge