Scientists at the Energy Research Centre of the Netherlands (ECN) have developed a bifacial tandem solar cell with a conversion efficiency of 30.2%.
They said the new cell device – created with Dutch consortium Solliance – was made by applying a newly developed perovskite cell on top of an industrial bifacial crystalline silicon version. Such an approach, say the scientists, enables a significantly higher power conversion efficiency as one cell is optimized for high energy photons, and the other low energy particles.
“The tandem device proposed here uses a four-terminal configuration, thus having separate circuits for the top and bottom cells that allow for dynamic fine tuning and optimization of the energy yield,” the creators of the cell wrote. The cell is also said to be better able to capture light on its front and rear sides by responding to the variability of incident light through its electronic design.
The researchers said they used the “bifacial-equivalent efficiency”, approach to measure the efficiency of the cell. That involves calculating the efficiency a monofacial device would require to generate the same amount of energy as the bifacial device annually, under the same operating conditions. According to that measurement method, the efficiency of the tandem cell was measured from the front in standard test conditions with another 20% of that illumination added from the rear. “By adopting this method, the bifacial equivalent tandem efficiency of our device is 30.2%, thus surpassing the limit of monofacial silicon solar cells,” said the researchers.
Prospect of 35% efficiency
The team believes the efficiency of its cell could reach 35% within three to five years. “We want to shorten the time to market and therefore we work together with our partners to make this technology ready for mass production,” said Gianluca Coletti, program manager for tandem technology at the ECN.
Solliance and the ECN announced last March they had achieved 26.3% efficiency on a transparent perovskite solar cell combined with a crystalline silicon cell. In April, Solliance announced a new record for its large area perovskite modules, which reached 14.5% conversion efficiency, and in January, it achieved 21.5% efficiency for a flexible copper indium gallium selenide (CIGS) tandem solar cell based on perovskite.
The ECN is working with Netherlands water management agency the Rijkswaterstaat – part of the Ministry of Infrastructure and the Environment – on the Solar Highways PV project, which deploys bifacial solar module technology on highways noise barriers.