China Sets Solar Cell Record at 28.04% Efficiency

Chinese researchers have shattered the world record for perovskite-organic tandem solar cell efficiency, achieving a certified steady-state photoelectric conversion rate of 28.04% — a breakthrough published in Nature on July 13 that brings lightweight, flexible solar power closer to everyday use. The team, led by Academician Li Yongfang and Professor Meng Lei at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS), solved a long-standing stability problem using an innovative “full-stage regulation” strategy with a photo-transformable additive molecule called TDB.

Why This Record Matters

Perovskite-organic tandem solar cells represent the next frontier in photovoltaic technology. Unlike conventional silicon panels, these cells stack two complementary light-absorbing layers: a wide-bandgap perovskite top layer that captures high-energy visible and ultraviolet photons, and a narrow-bandgap organic bottom layer that harvests near-infrared light. This tandem architecture allows the cell to convert a broader range of the solar spectrum into electricity, theoretically exceeding the ~33.7% Shockley-Queisser limit of single-junction devices.

According to China Daily, the technology promises a cheaper and easier route to mass manufacturing because the cells can be printed at low temperatures like ink on paper, unlike rigid silicon cells that require high-temperature fabrication.

The Breakthrough: From “Fearing Light” to “Controlling Light”

The key challenge holding back perovskite-organic tandem cells has been halide phase separation. To achieve the right bandgap, both iodine and bromine must be uniformly mixed into the perovskite crystal. But during fabrication and under continuous illumination, these halides tend to separate, creating defects that cause rapid performance degradation.

As reported by People’s Daily, Professor Meng Lei described the problem succinctly: “Wide-bandgap perovskite materials containing bromine and iodine have long had a ‘fear of light’ problem.”

The team’s solution was a molecule called TDB (4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzylamine), which operates in two stages. During fabrication, TDB slows the premature precipitation of the bromide-rich phase, ensuring uniform halide mixing during crystallization. Once the cell is operating under sunlight, the light transforms TDB into a new species (TAB) that binds strongly to perovskite grain boundaries, suppressing defect formation and blocking halide ion migration.

“The newly introduced photo-transformable additive molecule is precisely the key to achieving the transformation from ‘fearing light’ to ‘controlling light,’” Meng Lei told People’s Daily.

Record-Breaking Performance

The optimized wide-bandgap perovskite solar cell achieved an open-circuit voltage of 1.42 volts — a record for this class — and a fill factor of 85.13%. When integrated into a monolithic tandem device, the cell reached a peak efficiency of 28.80% in the lab, with a certified steady-state efficiency of 28.04%.

Equally important is the device’s stability. The Nature paper reports that the tandem cell retained 90% of its initial power conversion efficiency after 625 hours of continuous operation under the ISOS-L-1 protocol, demonstrating that high efficiency does not have to come at the cost of durability.

This surpasses the same team’s previous record of 26.4%, also published in Nature in 2024, representing a 1.64 percentage point improvement in just two years.

From Wearables to Space Stations

The lightweight, flexible nature of these cells opens up applications far beyond traditional solar farms. First author Wu Ruihan, a doctoral candidate at ICCAS, explained to People’s Daily that the cells “can be rapidly mass-produced through roll-to-roll printing like printing newspapers, with a thickness only a few tenths of conventional silicon cells, and can be bent, folded, or even cut into any shape.”

Potential applications include:

• Building-integrated photovoltaics: Windows, curtain walls, and curved roofs that generate power
• Wearable electronics: Clothing and backpacks that charge devices on the go
• Drones and UAVs: Extended flight duration through solar “skin”
• Space exploration: Satellites, space stations, and deep-space probes where weight is critical

Li Yongfang noted that the cells’ high specific power — power output per unit weight — is particularly valuable for aerospace. “Launch costs are calculated by the gram,” he said, as quoted by People’s Daily. “The lighter, the farther you can fly.”

China’s Growing Solar Leadership

This record is part of a broader pattern of Chinese dominance in next-generation solar technology. LONGi Green Energy holds the world record for perovskite-silicon tandem cells at 34.85% (NREL-certified, late 2024), while Professor Xu Jixian’s team at USTC set consecutive single-junction perovskite records reaching 26.7%. China already produces over 80% of the world’s solar panels, and the government has made perovskite commercialization a national priority under its 14th Five-Year Plan.

What’s Next

The research team’s “full-stage regulation” strategy using photo-transformable additives offers a promising pathway for further improvements. The next challenges include scaling the technology from lab-scale devices to commercial manufacturing processes like large-area roll-to-roll printing, and demonstrating long-term durability beyond 625 hours. If these hurdles can be overcome, perovskite-organic tandem cells could become a key technology in the global transition to clean energy.