Perovskite-silicon tandem solar cell with steric complementary design achieves 32.3% efficiency

Researchers in China developed a monolithic perovskite-silicon tandem solar cell using a steric-complementary interface design, achieving a certified efficiency of 32.12% and enhanced long-term stability. This strategy optimises molecular fit in the perovskite lattice, improving both charge transport and device longevity.

December 10, 2025 Emiliano Bellini

Image: Soochow University

From pv magazine Global

A group of researchers led by China’s Soochow University has fabricated a monolithic perovskite-silicon tandem solar cell with an interface design based on steric complementarity, aiming to improve device efficiency and reliability.

Steric complementarity defines how well the three-dimensional shapes of two molecules fit together without causing steric clashes, which are spatial overlaps that are physically impossible due to the atoms’ sizes. In perovskite solar cells, steric complementarity is key to the efficiency and stability of the material, which depends on how well the components fit together in the perovskite lattice.

“We introduced a new molecular-level strategy that moves beyond simply combining different molecules,” the research’s lead author, Wenhao Li, told pv magazine. “By deliberately selecting a pair of molecules with a significant size difference – a small, flexible piperazinium (PipI) cation and a large, rigid phenethyl ammonium (PEAI) cation – we created a synergistic effect.”

Li explained that the small PipI infiltrates deep into the perovskite surface to neutralize atomic-scale defects that are inaccessible to larger molecules, while the bulky PEAI simultaneously self-assembles into a robust, hydrophobic “canopy” on top, providing excellent protection against environmental stressors.

Through their Steric-Complementary Synergistic Strategy (SCSS), which reportedly resolves the structural trade-off between deep-level chemical passivation and the physical shielding needed by the perovskite absorber, the researchers built the top perovskite cell of the tandem device.

It was fabricated with a susbtrate made of indium tin oxide (ITO), a hole transport layer (HTL) made with a self-assembled monolayer known as 4PADCB, a perovskite absorber, the PMEAI passivation layer,a electron transport layer (ETL) relying on buckminsterfullerene (C₆₀), a tin oxide (SnOx) buffer layer, and a silver (Ag) metal contact.

Tested under standard illumination conditions, the device achieved a power conversion efficiency of 22.26%, an open-circuit voltage of 1.270 V, a short circuit current density of 21.50 mA/cm2 , and a fill factor of 81.52%. “This result demonstrates that SCSS can simultaneously suppress non-radiative recombination and optimise charge transport,” the academics emphasised.

The tandem cell, which was built with the perovskite device and a bottom heterojunction (HJT) silicon cell, achieved a maximum power conversion efficiency of 32.3% and a certified efficiency of 32.12%.

“This performance is among the highest reported for this technology, demonstrating the potency of our approach,” Li said. “The devices also exhibited outstanding long-term durability, retaining over 80% of their initial efficiency after 1,000 hours of continuous operation under maximum power point tracking. This demonstrates that our strategy not only boosts efficiency but also critically enhances device longevity.”

The new cell design was introduced in “Steric-Complementary Synergistic Strategy for High-Efficiency Monolithic Perovskite/Silicon Tandem Solar Cells,” published in Advanced Functional Materials.

“In summary, our study establishes a generalizable interface design principle based on steric complementarity, providing a promising pathway toward highly efficient and operationally stable perovskite-based tandem photovoltaics,” Li said.

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