Researchers from the University of Electronic Science and Technology of China, Sichuan Normal University, National University of Singapore and Northwestern University have developed a method to improve the long-term operational stability of perovskite/silicon tandem solar cells, even at elevated temperatures.
The team showed that a thin molecular layer used to connect the perovskite and silicon layers tends to degrade under heat, resulting in performance losses over time. To address this issue, the scientists designed a new heat-resistant version that holds the layers together more firmly, allowing the cells to maintain almost all their performance even after 1,200 hours of continuous operation at 65 deg C.
The team explained that previous studies mostly attributed performance loss to the perovskite material itself, but the researchers discovered that the real culprit is the ultra-thin contact layer linking the perovskite material to silicon. After recreating high-efficiency tandem architectures from the literature and testing them under sustained light and heat, they found that while the perovskite absorber remained stable, the thin “hole-transport” self-assembled monolayer (SAM) began to fail. This SAM gradually lost its orderly structure when heated, disrupting the flow of current through the device.
"Conventional SAMs act like a carpet of molecules that help charges move across," explained Assistant Professor Wei Mingyang, co-corresponding author of the study, from the Department of Materials Science and Engineering, College of Design and Engineering at NUS. "When they get too warm, the fibers start curling up, leaving gaps that block the flow of electricity."
To solve this, the team created a new and improved version of the SAM that could "lock" itself together into a sturdier network. The molecules form tiny chemical links with one another as they assemble, creating a tightly bound, cross-linked molecular contact that resists heat, stabilizes the interface between the layers and helps the entire solar cell retain high efficiency over time. With the new cross-linked layer in place, the perovskite - silicon tandem cells achieved efficiencies above 34%, including a certified 33.6% from an independent testing center, and retained over 96% of their initial performance after 1,200 hours of continuous illumination at 65 °C - a level of durability still rare in perovskite-based solar cells.
The results are a step toward practical, field-ready perovskite-silicon tandem panels that can generate more power from the same area of rooftop or solar farm while approaching the stability needed for real-world deployment.
