Engineering researchers strive to create cheaper, more efficient third-generation solar cells

Sandip Das, assistant professor of electrical engineering in the Southern Polytechnic College of Engineering and Engineering Technology, along with a team of three undergraduate research assistants, has recently fabricated the delicate solar cells, which are about 100 times thinner than a human hair.

The future of solar power generation is in these flexible solar cells, Das said. He and his research team are investigating various nano-materials to fabricate the third-generation solar cells. The researchers hope to develop a superior photovoltaic technology that produces cheaper and more efficient solar cells.

"The most fascinating part of doing this research is the enormous potential that this new technology offers, such as integrating flexible solar cells on wearable electronics, backpacks and self-charging cell phones and electricity-generating layers on windows, especially on skyscrapers, and solar power's ability to supply a large amount of clean, renewable and cheap energy for the future," said David Danilchuk, an electrical engineering major who is an undergraduate research assistant on the project.

In the laboratory, the research team fabricated the solar cells' multiple nano-structured layers using a unique manufacturing process. Specialty instruments, like electron microscopes, as well as X-ray spectroscopy techniques and precision electronic measurement systems, enable the research team to investigate and better understand the cells' behavior.

Baker Nour, an electrical engineering student and member of the research team, explained that the fabrication process developed by the team can produce these solar cells on plastic substrates to create flexible solar cells -- one of the most advanced ideas in solar technology today.

In practice, these flexible solar panels can be beneficial after catastrophic storms. Disaster relief personnel could transport rolled-up solar panels to produce portable power on site, Das explained. Commercial building developers also are eyeing smart building applications, like transparent solar panels for windows, so skyscrapers can generate solar power and be more energy efficient.

Innovative materials and efficiency

Current commercial solar panels use first-generation silicon solar cells, which are expensive, fragile and bulky, limiting their portability, according to Das.

The most promising materials systems for future generation solar cells, according to Das, are the materials that his research team applies in their fabrication -- an ultra-thin hybrid Perovskite noncrystalline film. Rather than using expensive silicon, they fabricate their solar cells on cheap glass substrates like those in windows and beverage bottles.

The team plans to explore the fabrication process so they can develop solar cells on flexible plastics or metal foils, without requiring expensive materials, million-dollar equipment or scientific-grade clean rooms.

"For the past 20 years, efficiency of silicon solar cells could not be improved much after substantial research efforts globally," Das said. He explained that silicon is not a good light absorber, and new technologies are needed to create high-efficiency cells at a lower cost. The new bandgap-engineered Perovskite crystals, which his team is investigating, can absorb a wider spectrum of sunlight compared to silicon, on a film that is 200 times thinner than silicon cells.

Implications for their research are still months away, but the team is confident that they will soon improve solar cells to attain higher efficiency, without the latest high-tech equipment or costly raw materials.

Cutting Costs

A major goal for their research is to substantially reduce the cost of producing solar cells.

Typically, solar cells are fabricated in a clean room, a controlled environment for manufacturing electronics that is free of dust or other contaminants. Even without a clean room, Das and his team are able to fabricate this next generation of solar cells and test their newly hatched cells.

"In the past 20 to 30 years of studying solar energy, researchers worldwide have learned how to cut costs tenfold," Das said. "The raw materials used for the third-generation solar cells are less expensive than the electronic-grade silicon."

A cutback in both material and fabrication costs means a significant reduction in the overall cost to produce electricity, ultimately saving consumers money.

"Our long-term goal is to bring the cost down to less than 10 cents per watt," Das said. In the U.S., silicon solar cells currently cost about 30 cents per watt.

Das predicts that by 2040 solar power will become mainstream as researchers develop technologies to more efficiently use available space for power generation and solar cells become cheaper.

"For us, it's exciting to be able to contribute to the field by sharing the knowledge that we obtain from our research and help advance the solar industry," Danilchuk added.