A research team led by the Chinese Academy of Sciences (CAS) has fabricated a perovskite-silicon tandem solar cell via a new passivation strategy that reportedly improve both device stability and efficieny.

“Our selective passivation process is fully compatible with existing crystalline silicon bottom cell manufacturing lines, as it does not require any modifications to the bottom cell fabrication steps,” corresponding author Weichuang Yang told pv magazine. “Moreover, the localized patterning is realized through a self-aligned templating approach that takes advantage of the natural pyramid morphology, without relying on complex lithography or exposure tools. This makes the technique promising for low-cost, large-scale manufacturing.”

The scientists explained that bottom silicon cells used in tandem devices have pyramid-textured silicon substrates that hinder uniform perovskite coating, causing localized electrical leakage and limiting tandem cell performance.

To address this issue, they proposed to use a peak-selective passivation (PSP) strategy that utilizes polystyrene nanospheres as a sacrificial template to achieve spatially localized deposition of aluminum oxide (Al₂O₃) on the apex regions of submicron silicon pyramids. This targeted coating selectively insulates and passivates the high-curvature pyramid peaks, effectively mitigating local electric field concentration and suppressing potential electrical shunting pathways.

Importantly, Al₂O₃ exhibits only weak interaction with the self-assembled monolayers (SAMs), allowing the underlying functional surface to remain accessible for subsequent perovskite growth. This interfacial compatibility promotes direct contact between the perovskite absorber and the SAM-modified silicon surface while simultaneously providing additional heterogeneous nucleation sites, thereby enhancing perovskite crystallization and coverage quality.

As a result, a pinhole-free and conformal perovskite layer is achieved on the pyramid-textured silicon substrate, which facilitates efficient carrier transport across the interface and significantly suppresses non-radiative recombination losses.

Tested under standard illumination conditions, a 1 cm2 perovskite-silicon tandem cell built through the new passivation process achieved a maximum efficiency of 33.33% and a certified efficiency of 32.89%. The name of the certification body was not disclosed. “The device also retained about 90% of its initial efficiency after 1,000 hours of continuous operation, demonstrating excellent long-term stability,” said Yang.

The new passivation tech and the cell design were presented in the study “Selective passivation of pyramid peaks for 32.9%-efficient perovskite/silicon tandem solar cells,” published in Matter. The research team comprised scientists from China’s Ningbo Institute of Materials Technology and Engineering (NIMTE), Soochow University, Taizhou University, and S.C Exact Equipment Co.