“If you want to make solar competitive, you need to make solar cells more efficient and cost-effective,” said Bag.
Inspired by the concept of newsprint where rolls of paper are printed with ink to create newspapers, Bag and his team looked for alternatives to inorganic, hard silicon in search of a material able to transform solar into energy – and be printed in the process.
“Silicon cells use purely inorganic materials, which by nature are very hard,” said Bag. “We needed a material that was easy to print and at the same time able to capture sunlight. We determined an inorganic-organic hybrid material would be easy to print and could still harvest solar energy.”
Bag’s material of choice, thin-film perovskites, have an excellent light-absorbing capability and power conversion efficiencies that have improved tremendously compared to the more than 30 years it took for silicon solar cells to improve to today’s levels. Only recently has this material been explored for its solar power ability, with Bag among the researchers expanding the field.
“The material has been around since the 1990s and was used to make test-level, light-emitting diodes. Researchers knew it had solar ability, but this was not the focus at the time,” said Bag.
In Bag’s study, perovskite precursor material was atomized using ultrasonic waves to form extremely fine, aerosol droplets able to be transferred into the print nozzle of an aerosol-jet spray printer. Using computer-aided design tool paths, a surface was then coated with the material using the direct-write printer, forming a solar cell with a 15.4 percent efficiency on a flat surface.
Bag and his team also demonstrated the ability to print these solar cells on a 3-D surface with a 5.4 percent efficiency – marking the first time this has been shown in the field of printed photovoltaics.
“We have not optimized conditions for 3-D printing of these yet, but we know it can be done. Once you know how to print it, it has huge potential for other applications,” said Bag.
For the Air Force, the applications for this material and the new printing process are enormous. The method can be used to print flexible solar cells on clothing, to create self-powered robotics and light-emitting devices and even to make flexible, self-powered sensors, to name a few.
Bag, along with fellow researchers Dr. Michael Durstock, Soft Matter Materials branch chief at the AFRL Materials and Manufacturing Directorate, and James Deneault, a research engineer at Universal Technology Corp., have filed a patent application for the technology. Though this research is still in its early stages, the impact of the new manufacturing processes has great potential for the future.
“Understanding ways to make and print this material more efficiently at the most basic level can lead to future cost savings,” Bag concluded.
Dr. Santanu Bag, a project scientist at the Materials and Manufacturing Directorate, Air Force Research Laboratory, is exploring cost-efficient manufacturing of solar cells using additive technology. (U.S. Air Force photo/David Dixon)
Researchers at the Materials and Manufacturing Directorate, Air Force Research Laboratory, have demonstrated the ability to print solar cells on three-dimensional surfaces using a modified aerosol spray printer. The ability to print three dimensionally opens the aperture for future application of solar cells on diverse surfaces for sensors, robotics and more. (U.S. Air Force photo/David Dixon)