China Smashes Solar Record with 28.04% Tandem Cell

Chinese researchers at the Institute of Chemistry, Chinese Academy of Sciences (CAS), have achieved a world-record 28.04% certified steady-state power conversion efficiency in perovskite-organic tandem solar cells, marking a significant leap forward for next-generation photovoltaic technology. The breakthrough, published in Nature on July 13, 2026, simultaneously addresses both the efficiency ceiling and the stability challenges that have long hindered this class of solar cells.

The research team, led by Academician Li Yongfang and Professor Meng Lei, introduced a novel “photo-transformable” additive molecule that enables a two-stage stabilization strategy—improving film quality during fabrication and dynamically stabilizing the material during operation.

The Tandem Advantage

Perovskite-organic tandem solar cells stack two light-absorbing layers with complementary capabilities. A wide-bandgap perovskite top cell absorbs high-energy ultraviolet and visible light, while a narrow-bandgap organic bottom cell captures the near-infrared spectrum that passes through. This design allows the cell to harvest a broader range of sunlight than any single-junction cell, surpassing the theoretical efficiency limits of conventional silicon solar cells.

According to PV Magazine, these tandem cells are solution-processable, making them suitable for large-area, flexible, lightweight manufacturing through roll-to-roll printing and slot-die coating. This opens the door to applications where traditional glass-based panels are impractical, including building-integrated photovoltaics, portable electronics, wearables, drones, and aerospace systems.

Solving the ‘Light Fear’ Problem

The critical challenge for high-bromine-content wide-bandgap perovskites has been “halide phase separation”—a phenomenon where iodide and bromide ions within the material migrate and segregate under illumination, forming iodine-rich and bromine-rich regions. This degrades voltage output and long-term stability, causing the cells to deteriorate rapidly when exposed to light.

“This study’s key technical challenge was how to make high-bromine-content wide-bandgap perovskites transition from ‘fearing light’ to ‘harnessing light,’” said Professor Meng Lei, a researcher at the CAS Institute of Chemistry, as reported by Guangming Net.”The newly introduced TDB molecule is the key to achieving this transformation—stabilizing the mixed-halide phase during crystallization and converting into a stronger anchoring and passivation molecule during light operation.”

The team designed a photo-transformable additive molecule called 4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzylamine (TDB), which serves a dual function. During crystallization, TDB improves halide distribution homogeneity by suppressing the rapid precipitation of the bromine-rich phase. During operation, light exposure transforms TDB into a new species (TAB) that binds more strongly to perovskite grain boundaries, suppressing ion migration and defect formation.

Record-Breaking Performance

The optimized wide-bandgap perovskite single-junction solar cell achieved a power conversion efficiency of 20.01%, an open-circuit voltage of 1.42 V, and a fill factor of 85.13%—all records for this bandgap range. When integrated into a tandem configuration, the device reached a peak efficiency of 28.80%, with an independent third-party certification confirming a steady-state efficiency of 28.04%.

Equally important is the stability improvement. The device retained 90% of its initial efficiency after 625 hours of continuous operation under the ISOS-L-1 illumination protocol—a critical advancement since previous perovskite-organic tandems suffered from rapid degradation under light.

This represents a significant leap from the team’s previous milestone in 2024, when they achieved 26.4% efficiency (certified 25.7%) using surface passivation techniques. The new result marks a 2.34 percentage point absolute improvement in certified efficiency over two years.

Broader Implications

Academician Li Yongfang highlighted the transformative potential of this technology: “Perovskite-organic tandem solar cells combine lightweight, flexible, and high-specific-power advantages. This research will provide new scientific and technological pathways for further energy structure transformation and sustainable development.” He noted that the technology could find applications in buildings, transportation, wearable electronics, and even aerospace—including satellites, space stations, and deep-space exploration, as reported by Guangming Net.

China is already the world’s largest manufacturer and installer of solar panels, dominating over 80% of global solar module production. This breakthrough reinforces China’s position at the forefront of solar technology R&D, potentially extending its leadership into next-generation photovoltaic technologies.

What’s Next

While the results are impressive at the laboratory scale, several questions remain before commercialization. Can this 28.04% efficiency be reproduced in large-area devices suitable for commercial production? Will the TDB additive strategy work at scale with roll-to-roll manufacturing processes? And what are the long-term degradation characteristics under real-world outdoor conditions over multiple years?

The research was published in Nature (DOI: 10.1038/s41586-026-10869-x) under the title “Perovskite–organic tandem solar cells with a photo-transformable stabilizer.” As the scientific community works to replicate and build upon these findings, the path toward commercially viable next-generation solar cells appears brighter than ever.