How a Chinese Team Reached 28.04% Efficiency in Perovskite–Organic Tandem Solar Cells

A team at the Institute of Chemistry of the Chinese Academy of Sciences, led by academician Li Yongfang and researcher Meng Lei, has reported a certified steady-state power-conversion efficiency of 28.04% for a perovskite–organic tandem solar cell. The result was described as a world record for this class of device. The underlying Nature study was published on July 13, 2026, rather than August 21. 1820

The result matters for more than the headline efficiency. The team also targeted one of the main weaknesses of wide-bandgap perovskites: their tendency to undergo light-induced halide phase segregation, which can reduce performance during operation.

The record in brief

The reported monolithic tandem cell reached a peak efficiency of 28.80%, with a certified steady-state efficiency of 28.04%. 18 A separate report from the Chinese Academy of Sciences describes the wide-bandgap perovskite top subcell as having achieved an unusually high open-circuit voltage for its type before integration with the organic bottom cell. 26

The device also retained 90% of its initial efficiency after 625 hours of continuous illumination, according to reports from the team’s institute and Chinese state media. 1828

Those figures should be read as laboratory-cell results, not as evidence that the technology is already ready for commercial deployment or spaceflight.

Why tandem architecture helps

A tandem solar cell stacks two photoactive subcells with different light-absorption ranges. In this design, the wide-bandgap perovskite subcell sits above an organic subcell.

• The wide-bandgap perovskite top cell is suited to absorbing higher-energy portions of sunlight.
• The organic bottom cell can capture lower-energy light that passes through the perovskite layer.

Using the two materials together can improve spectrum utilization compared with relying on one absorber alone. Reports on perovskite–organic tandems describe the architecture as a combination of a wide-bandgap perovskite subcell and a narrower-bandgap organic subcell connected in series. 25

The organic layer’s material characteristics may also help shield the perovskite portion from some environmental exposure, although the extent of that protection depends on the complete device stack and operating conditions.

The materials strategy: controlling defects throughout the device’s lifecycle

Mixed-halide, wide-bandgap perovskites are attractive for tandem cells because their bandgap can be tuned to complement a lower-bandgap rear cell. Their stability under illumination, however, remains a central challenge.

The CAS team’s approach was described as full-stage regulation: rather than addressing defects only after a film has been formed, the researchers aimed to control defect-related processes during material preparation, film growth, and subsequent operation. The strategy used a photo-transformable additive to help stabilize the mixed-halide perovskite phase. 171821

The objective was to suppress the light-driven redistribution of halide ions that can create regions with different bandgaps. By limiting that phase segregation, the team sought to preserve both the perovskite subcell’s voltage and the tandem device’s output during illumination. 1718

This lifecycle-oriented approach is significant because efficiency and stability are tightly linked in wide-bandgap tandem devices. A record measured at the start of a test is less useful if the active layer rapidly changes under operating light.

Why flexible and lightweight solar applications are being discussed

Perovskite and organic photovoltaic layers can be deposited from solution, creating a possible route toward coating-based manufacturing. In principle, techniques such as slot-die coating or roll-to-roll processing could support lightweight, thin, and mechanically adaptable devices, although the record result itself does not demonstrate commercial-scale production.

Earlier work in the field has already reported both rigid and flexible perovskite–organic tandem devices, showing why researchers view the architecture as relevant to flexible photovoltaics. 10

Potential use cases include:

• photovoltaics integrated into curved building surfaces;
• wearable or conformable power sources;
• lightweight power systems for drones; and
• aerospace structures where mass and stowage volume matter.

The practical advantage in these settings may not be maximum efficiency alone. A solar device that is light, foldable, or able to conform to a curved surface could be useful where conventional rigid panels are difficult to install or transport.

Could the technology power rollable satellite arrays?

The concept is plausible enough to justify further research: lightweight, flexible solar arrays could potentially be folded or rolled for launch and deployed in orbit. But the reported 28.04% efficiency should not be treated as proof of satellite readiness.

Space deployment would require testing beyond continuous illumination on a laboratory bench, including:

• tolerance to ultraviolet and particle radiation;
• stability in vacuum and control of outgassing;
• resistance to repeated thermal cycling;
• mechanical durability during launch, deployment, and operation; and
• consistent performance across larger areas and interconnected modules.

The available reports establish a certified efficiency record and an illumination-stability result. They do not establish qualification for the space environment. That distinction is essential when moving from a small-area champion cell to a flight system.

What comes next

The next engineering milestone is likely to be reproducible scale-up: translating the small-area record into uniform sub-modules, then into flexible modules with reliable interconnections and encapsulation.

Researchers will also need to measure how the full device behaves under realistic combinations of heat, light, humidity, bending, vacuum, and radiation. A high-performing cell becomes a deployable product only when its performance can be repeated across larger areas and maintained through the stresses of its intended application.

The CAS result therefore represents two advances at once: a 28.04% certified steady-state efficiency record for perovskite–organic tandems and a materials strategy aimed at making wide-bandgap perovskites more stable under light. Its broader importance will depend on whether those gains survive manufacturing scale-up and application-specific reliability testing.