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Huang increases organic solar cells’ efficiency with ferroelectric polymer layers

When a child’s video game battery runs low, parents may tell the child to go play outside. In a few years, playing that video game outside could actually recharge the game's power supply from sunlight, with an innovation developed at the University of Nebraska-Lincoln College of Engineering.

Jinsong Huang, assistant professor of mechanical engineering, applied ferroelectric polymer layers in the structure of organic solar cells, to make energy harvesting more efficient and with less expensive materials. The innovation was also reported by the prominent scientific journal Nature Materials in its Feb. 13 online edition.

Ferroelectric polymers have pairs of electrically charged molecules that align to make a large, permanent electromagnetic electric field, similar to how magnetic atoms line up in ferromagnetic materials to produce a large permanent magnetic field, said Huang’s collaborator Steve Ducharme, vice-chair and professor of Physics & Astronomy at UNL, who leads a lab that specializes in ferroelectric polymers.

When the molecules align they can point in the same direction and generate enormous electric fields. Huang’s work married this effect to photovoltaics such as organic solar cells: adding a thin layer of ferroelectric polymers to augment the electrical field, which enhances performance inside the material.

“The performance with those materials amazed us,” Huang and Ducharme said. This development could result in organic solar cell material that is lightweight and flexible enough to create lower-cost devices such as solar panels for more extensive use on homes and public buildings.

Solar cells now made of silicon yield an efficiency of 10-15% but currently the cost is still too high for widespread use, said Huang. The ferroelectric polymers help organic solar cells to be produced likely 10 times cheaper than traditional silicon solar cells, Huang said, with efficiency that can theoretically reach or surpass silicon products. Greater efficiency in photovoltaic devices makes more energy available from the charging process.

One of the biggest challenges to organic solar cells’ efficiency is getting the charge out of the light-gathering device. Yongbo Yuan, a post-doctoral researcher on Huang’s team, works to extract the light-energized electrons inside the organic solar cells. When the augmented electric field separates the electrons from their traps, electrons can easily flow out of the solar cell devices and increase the electricity output.

Adding the ferroelectric polymer layer achieves this by pulling the charges out of Huang’s solar cell material to more efficiently extract the power. Huang’s team demonstrated that ferroelectric polymer layers increased efficiency in several types of organic photovoltaic devices threefold, from only 1–2% without the ferroelectric layers to 4–5% with the ferroelectric layers.

Huang said efficiency has already increased further, to 5-7% with several types of polymer semiconductor materials evaluated. With his team’s further collaboration in testing the organic solar cells’ structure and light-absorbing polymer components, he expects efficiency surpassing 15% in coming years.

Jinsong Huang innovates ferroelectric polymers in organic solar cells

Photo: Assistant Professor Jinsong Huang advances organic solar cell materials development in his lab at the University of Nebraska-Lincoln College of Engineering. Huang's innovation applies ferroelectric polymer layers in organic solar cells, a breakthrough that greatly increases the energy efficiency of these photovoltaic devices—which also have lower manufacturing costs—versus traditional silicon-based products.