Softer perovskite lattices yield stable bifacial tandem solar cells

Bifacial perovskite/silicon tandem solar cells that capture light from both faces could deliver more power per unit area than conventional panels, but keeping their perovskite layer stable under real operating conditions remains a central obstacle. A new study published in Nature Energy points to a materials property the authors call perovskite lattice compliance—the capacity of the crystal lattice to elastically accommodate stress—as a physically testable descriptor of how well these absorbers withstand combined light and heat exposure.

The researchers worked with perovskite absorbers of roughly 1.55 electronvolt bandgap. This compositional choice reduces reliance on bromide, which largely mitigates light-induced halide segregation and shifts the dominant stability challenge to the intrinsic photothermal resilience of bromide-lean absorbers. Across the compositions studied, higher lattice compliance promoted photothermal stability by suppressing the accumulation of thermally induced microstrain, shifting deep-level defects towards shallower states and reducing disorder in the band-edge energetics.

Guided by this absorber-level design principle, the team fabricated bifacial monolithic perovskite/silicon tandem devices. Under illumination equivalent to a ground albedo of 0.20, the tandems achieved a power-generation density of 36.2 milliwatts per square centimetre. In ISOS-L-2 ageing tests—one-sun illumination at 65 degrees Celsius—the cells retained 90 percent of their initial efficiency after more than 1,000 hours of operation.

The authors suggest the findings establish lattice compliance as a physically testable framework for designing stable perovskite absorbers, offering researchers a measurable criterion for screening compositions rather than relying on trial-and-error stability testing. Because the descriptor links mechanical response of the lattice to defect energetics and microstrain evolution, it connects the photothermal durability of bromide-lean absorbers to an underlying materials property that can be evaluated directly.

The work, led by Fuzong Xu, Jiang Liu and Xuechun Zhang with colleagues including Stefaan De Wolf, was published on 29 October 2026. As with any laboratory study, the reported efficiency and stability figures come from controlled test conditions, and translating the lattice-compliance design principle into commercially manufactured bifacial tandem modules will require further validation at scale.

Subject of Research: Lattice compliance as a design principle for stable bifacial perovskite/silicon tandem solar cells

Article Title: Perovskite lattice compliance enables efficient and stable bifacial perovskite/silicon tandem photovoltaics

Article References: Xu, F., Liu, J., Zhang, X., Hnapovskyi, V., Yavuz, I., Deger, C., Li, W., Razzaq, A., Xu, L., Vishal, B., Chen, J., He, M., Marengo, M., Miao, T., Li, C., Prasetio, A., Pininti, A., Liu, Z., Allen, T., … De Wolf, S. (2026). Perovskite lattice compliance enables efficient and stable bifacial perovskite/silicon tandem photovoltaics. Nature Energy. https://doi.org/10.1038/s41560-026-02162-y

Image Credits: AI Generated

DOI: 10.1038/s41560-026-02162-y

Keywords: perovskite, silicon tandem, bifacial solar cells, lattice compliance, photothermal stability, halide segregation, ISOS-L-2, power-generation density, microstrain, defect physics, lattice, compliance