A new charge transport layer has enabled all-perovskite triple-junction solar cells to achieve 27.3% efficiency while maintaining more than 90% of their initial performance after 770 hours, marking a significant step toward commercially viable high-efficiency photovoltaics.
Progress in perovskite photovoltaics
After all-perovskite tandem solar cells set a new efficiency benchmark earlier this year, triple-junction perovskite solar cells are now making headlines. The breakthrough comes from a research team led by Germany’s Helmholtz-Zentrum Berlin (HZB) für Materialien und Energie, which redesigned one of the device’s internal layers to deliver not only higher efficiency for this photovoltaic architecture, but also exceptional operational stability.
Achieving long-term stability remains one of the greatest challenges facing synthetic perovskite semiconductors, making the new results particularly significant.
A new generation of multijunction photovoltaics
As conventional silicon solar cells approach their theoretical efficiency ceiling, multijunction photovoltaics continue to attract growing interest. While single-junction solar cells are theoretically limited to 33.7% efficiency, double-junction and triple-junction architectures can theoretically reach 44% and 52%, respectively.
The concept is straightforward. These photovoltaic “sandwiches” combine semiconductor materials with different band gaps, allowing them to absorb a broader portion of the solar spectrum. As a result, they significantly reduce transmission and thermalization losses that occur when incoming photons have either less or more energy than the semiconductor’s band gap.
Within this field, perovskites offer additional advantages, including lower manufacturing costs, mechanical flexibility, reduced material consumption, and the ability to precisely tune their band gap for each subcell.
All-perovskite multijunction solar cells
Research into all-perovskite multijunction solar cells has already produced remarkable results. In May 2026, the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences achieved 30.3% power conversion efficiency using a monolithic two-terminal tandem configuration.
The researchers addressed one of the fundamental challenges of perovskite materials: different layers tend to crystallize at different rates, creating structural and compositional inhomogeneities that reduce device performance. By introducing new additives, the team improved light-to-electricity conversion while preserving 92% of the initial efficiency after 1,000 hours of operation.
Even so, all-perovskite multijunction photovoltaics still struggle with long-term operational stability. A 1,000-hour laboratory test represents only a fraction of the lifetime required for commercial deployment.
Improving the HTL in triple-junction perovskite solar cells
The HZB researchers tackled this limitation using a 100% triple-junction perovskite solar cell. Their attention focused on the hole transport layer (HTL), the selective material positioned next to the perovskite absorber that extracts positively charged carriers.
In tin-lead (Sn-Pb) perovskite solar cells, the standard HTL is the polymer PEDOT:PSS. However, this material presents significant drawbacks. Because of its thickness, it causes parasitic photon absorption that lowers current generation. In addition, its acidic and hygroscopic nature accelerates degradation of the Sn-Pb perovskite, promoting oxidation of internal materials and shortening device lifetime.
To replace PEDOT:PSS, the researchers turned to self-assembled monolayers (SAMs), large organic molecules that promise almost no parasitic absorption and improved stability. In practice, however, SAMs transport holes much less efficiently than PEDOT:PSS, particularly in triple-junction devices. As a result, triple-junction perovskite solar cells using conventional SAMs had never exceeded 16% efficiency.
Why do these molecules perform so poorly? According to the researchers, conventional SAMs create ionic losses at the interface, forming an internal electrical barrier that limits charge extraction. To overcome this issue, the team introduced a thin layer of graphene oxide (GO) beneath the SAM, improving both the morphology and electronic properties of the interface.
The results
“With triple-junction solar cells, we achieved an efficiency of 27.3%, one of the highest values reported for this technology,” said HZB researcher Steve Albrecht.
The GO/SAM devices also demonstrated outstanding operational stability, retaining more than 90% of their original efficiency after 770 hours of continuous operation, establishing a new stability record for this solar cell architecture.
“Our analyses suggest that by further improving the quality of the individual perovskite layers and the interlayer films, the efficiency of this architecture could be increased to more than 30%.”
The study, “Triple-junction all-perovskite solar cells with self-assembling hole contacts in all subcells,” was published in Joule (2026). DOI: 10.1016/j.joule.2026.102575.
