Bifacial Perovskite Solar Cells Show Promise for Increased Efficiency, Lower Costs, Finds NREL Study

Scientists at NREL Harness Reflected Light to Boost Energy Yields of Perovskite Solar Cells

In a breakthrough study conducted at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), researchers have uncovered the potential of bifacial perovskite solar cells to revolutionize the renewable energy landscape. By allowing sunlight to reach both sides of the device, these solar cells demonstrate the capability to generate higher energy yields at reduced costs.

Unlike their monofacial counterparts, bifacial solar cells possess a dual nature that enables the capture of direct sunlight on the front and the harnessing of reflected sunlight on the back. This unique feature gives them a significant advantage in terms of overall performance.

Kai Zhu, a senior scientist in the Chemistry and Nanoscience Center at NREL, and the lead author of a paper recently published in the journal Joule, stated, “This perovskite cell can operate very effectively from either side.” The research team, which includes co-authors from NREL such as Qi Jiang, Rosemary Bramante, Paul Ndione, Robert Tirawat, and Joseph Berry, as well as collaborators from the University of Toledo, has made significant progress in developing highly efficient bifacial single-junction perovskite solar cells.

Earlier attempts at bifacial perovskite solar cell research fell short in comparison to monofacial cells, which boast a current record of 26% efficiency. The NREL researchers aimed to create a bifacial cell that matches the front-side efficiency of the best-performing monofacial cell while maintaining a similar efficiency on the back side.

Through meticulous construction and optical and electrical simulations, the team succeeded in producing a solar cell with closely matched efficiency under illumination from both sides. The front-side illumination achieved an efficiency exceeding 23%, while the back-side illumination reached approximately 91% to 93% of the front.

To determine the optimal thickness for the perovskite layer on the front and the rear electrode, researchers relied on simulations prior to constructing the cell. A delicate balance had to be struck, with the perovskite layer needing to be thick enough to absorb most photons from a specific part of the solar spectrum, but not so thick as to block the photons. The rear electrode’s thickness was also carefully determined to minimize resistive loss.

Zhu emphasized that simulations played a crucial role in guiding the design of the bifacial cell, saving significant time and resources that would have been spent on experimental trial and error. The team determined that an ideal perovskite layer thickness is approximately 850 nanometers, about 1/82 the thickness of a human hair.

To evaluate the efficiency gains enabled by bifacial illumination, the researchers placed the solar cell between two solar simulators. The front side received direct light, while the back side was exposed to reflected light. As the ratio of reflected light to front illumination increased, the cell’s efficiency climbed accordingly.

While it is estimated that manufacturing a bifacial perovskite solar module may initially incur higher costs compared to a monofacial module, the long-term benefits are promising. Bifacial modules have the potential to generate 10% to 20% more power, making them potentially better financial investments.

Funding for this groundbreaking research was provided by the U.S. Department of Energy Solar Energy Technologies Office, highlighting the government’s commitment to advancing solar energy technologies and sustainable power generation.