Flexible Tandem Solar Cells Achieve 24.6% Efficiency

The bonding between layers in flexible solar cells was improved, making them more efficient, durable, and ready for commercial use.

Researchers from the Chinese Academy of Sciences have improved the efficiency and durability of flexible tandem solar cells by strengthening the bond between the top and bottom layers. Copper indium gallium selenide (CIGS) is already used in commercial solar cells thanks to its tunable bandgap, strong light absorption, low sensitivity to temperature, and stable performance. These features make it a strong candidate for the bottom layer in next-generation tandem solar cells.

In flexible perovskite/CIGS tandem cells, a perovskite top layer captures sunlight efficiently, while the CIGS bottom layer supports overall performance. This combination offers promise for lightweight, high-efficiency solar technologies. But CIGS has a rough surface, which makes it hard to form a high-quality perovskite layer on top. This challenge has limited the commercial potential of such tandem cells.

– Advertisement –

The researchers separated the steps of self-assembled monolayer (SAM) adsorption and dissolution while also introducing perovskite seeding. A high-polarity solvent was used to avoid SAM clustering during dissolution, and a low-polarity solvent acted as an antisolvent to help form a dense SAM during adsorption. They also added a pre-mixed seed layer to improve the surface wettability and crystal quality of the perovskite, ensuring better adhesion.

Using this method, the team built a 1.09 cm² flexible monolithic perovskite/CIGS tandem solar cell. The device reached a stabilized efficiency of 24.6% (certified at 23.8%), rivaling top rigid designs and marking one of the highest efficiencies recorded for flexible thin-film solar cells.

Even after 320 hours of use and 3,000 bending cycles at a 1 cm radius, the cell maintained over 90% of its original efficiency—showing strong mechanical durability and long-term stability.

This breakthrough supports the future development of cost-effective, high-performance flexible tandem solar cells and brings them closer to commercial use.

Reference: Nature Energy (2025). DOI: 10.1038/s41560-025-01760-6