Office of Energy Efficiency & Renewable Energy

Iris PV and NREL Work to Modernize Rooftop Solar Production with Tandem Solar Panels

February 8, 2018

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Inkjet-printed perovskite solar cells
Inkjet-printed perovskite solar cells with efficiency above 16%.
Dr. Maikel van Hest, National Renewable Energy Laboratory

Did you know there are alternatives to standard silicon solar panels? Or that someday soon, you might be able install a solar panel that is 50% more efficient than the average silicon photovoltaic (PV) solar panel?

That’s exactly what Iris Photovoltaics, Inc. (Iris PV) is aiming to produce. The Berkeley, California-based company is working to modernize how silicon solar panels are manufactured. In addition, they are attempting to increase the efficiency of PVs to a range of 25-30%.

The U.S. Department of Energy (DOE) Small Business Vouchers (SBV) program award recipient’s technology adds a crystalline metal-halide perovskite layer to coat standard silicon solar panels, which produces additional electricity from infrared light. This is then layered on top of traditional silicon solar cells to create a “tandem” solar panel. These “tandem” solar panels, composed of two materials instead of one, generate a greater amount of electricity per panel.

From Manufacturing Floor to Rooftops

Iris PV is receiving technical assistance from researchers at the National Renewable Energy Laboratory (NREL) through SBV as part of DOE’s Office of Energy Efficiency and Renewable Energy Technology-to-Market program. Iris PV cofounders Colin Bailie and Chris Eberspacher are working with NREL researchers to manufacture the technology at scale and accelerate the adoption of solar with their high-efficiency PV products.

“Through the SBV program, we are addressing critical manufacturing challenges so that production facilities can be built,” said Bailie.

“Commodity silicon solar cells are mired in the 18-22% efficiency range. The theoretical maximum for combining two solar cell materials is 46% efficiency, though we’re aiming to fly a little less close to the sun and hit 30-35% efficiency.”

Compared to today’s standard solar panel, Iris PV’s design minimizes costs for manufacturers and is compatible with most existing PV technologies. It could also save individual homeowners thousands of dollars in upfront costs and utility bills compared to current technology. Once this technology is commercially available, we hope to get an enthusiastic response from both solar installers and homeowners,” said Bailie.

Overcoming Manufacturing Challenges

Today’s metal-halide perovskite solar cells have manufacturing limitations. Specific manufacturing techniques, such as spin-coating, limit the size of individual glass panels. The spin-coating process deposits thin layers of solvents or coating materials, like silicon wafers, using centrifugal force. This process also requires additional patterning in solar cell production, adding to overhead costs.

With the technical assistance of NREL’s researchers, Iris PV is overcoming these limitations using inkjet printing. Inkjet printing can uniformly coat large areas and complete patterns by dispensing single drops with controlled print design. Because inkjet printers are more precise than spin-coaters, the production process is more efficient and uniform.

According to Iris PV, inkjet printing allows for rapid prototyping and low-cost custom products down the road, including the Iris PV form factor. To date, the project has printed single-junction perovskite cells with efficiencies of more than 16%, on par with devices made using other scalable technologies. And another benefit to Iris PV’s tandem panel design: Because it will be compatible with existing manufacturing tools and methods, costs for current solar manufacturers to switch technologies will be minimal.

Iris PV’s next step is to demonstrate the technology’s scalability. If they are able to print perovskite films on a 6” x 6” area, the demonstration will be considered a success.

As for Bailie and Eberspacher, their team especially valued the support of NREL researchers who helped through the SBV program--Maikel van Hest, Rosie Bramante, and James Whitaker.

“The development of inkjet-printed perovskite photovoltaics would not have been possible without the support provided by the Department of Energy’s Small Business Vouchers program,” said Bailie.