Precision interface chemistry pushes perovskite solar cells beyond 26% efficiency

Precision Interface Chemistry Drives Perovskite Efficiency

Researchers have achieved a significant milestone in photovoltaic technology, reporting perovskite solar cell (PSC) efficiencies exceeding 26%. By employing advanced interface engineering and chemical additives, teams have successfully addressed long-standing obstacles related to defect density and structural degradation that previously limited the performance and stability of these devices.

According to recent reports, a research team led by the Qingdao Institute of Bioenergy and Bioprocess Technology of the Chinese Academy of Sciences (CAS) developed a method to create an ultra-thin two-dimensional (2D) perovskite layer within conventional three-dimensional (3D) devices. This approach reduces defect concentrations at buried interfaces by more than 90 percent. By suppressing these defects—which typically act as recombination centers that lower power output—the researchers have sharply improved both device performance and long-term operational stability.

Targeted Interface Engineering

A primary challenge in PSC development is the formation of high-density defects on the top and bottom surfaces of the perovskite layer. Historically, researchers attempted to mitigate these defects by adding long-chain ammonium salts to the perovskite precursor. However, this often resulted in the unintended formation of 2D structures throughout the entire bulk of the film, rather than just at the critical interfaces.

To gain precise control, the CAS-led team developed a new electron transport layer using tin dioxide (SnO₂) nanoparticles grafted with thioglycolic acid (TGA) and oleylamine (OAm). This modified layer, known as SnO₂-TGA-OAm, remains stable until the thermal annealing of the perovskite layer. At that stage, a cation exchange with formamidinium iodide (FAI) triggers the spontaneous formation of a 2D/3D heterostructure exclusively at the buried bottom interface. This targeted engineering allows for improved performance without disrupting the internal crystal structure of the solar cell.

Scalability and Performance Metrics

The research team validated the effectiveness of this interface engineering across multiple device scales:

| Device Area | Power Conversion Efficiency (PCE) |
| :— | :— |
| 0.09 cm² | 26.19% |
| 21.54 cm² | 23.44% (Certified: 22.68%) |
| 64.80 cm² | 22.22% |

Zhao Qiangqiang, the first author of the study, noted that these values rank among the highest reported for small-sized PSCs and modules using 2D/3D heterojunctions. The team emphasized that this in situ solid-state ligand-exchange process is designed to be compatible with industrial manufacturing, potentially accelerating the commercialization of perovskite photovoltaics.

Ferroelectric Decoration and the Efficiency Limit

In parallel efforts to reach the Shockley-Queisser (SQ) efficiency limit, other researchers have utilized “ferroelectric buried heterojunction” (FBHJ) architectures. By integrating ferroelectric perovskites—specifically 4AMP-DJ and DDFP-RP—into their devices, scientists successfully pushed efficiencies to 26.62%.

Systematic characterization revealed that these additives improved the open-circuit voltage (VOC) and fill factor (FF) of the cells. A champion device with an aperture area of 0.0718 cm² achieved a certified efficiency of 26.07%, verified by the Fujian Metrology Institute. According to the study, this configuration minimizes energy loss to 0.35 eV, which is near the theoretical limit for the material’s bandgap. These devices also demonstrated significant resilience, maintaining high performance during maximum power point tracking under continuous illumination.

Future Outlook for Perovskite Technology

Despite the rapid progress, the field continues to focus on three major areas: further efficiency gains, enhanced durability, and the establishment of scalable production. Current research into composition engineering—fine-tuning the optical bandgap through multicomponent A- and X-site ions—remains a key strategy for customizing perovskite properties.

Furthermore, researchers are focusing on the quality of crystal growth. By utilizing solvents and additives to manage the evaporation rate and nucleation process, the industry aims to produce uniform films with minimal grain boundaries. As these techniques move from controlled laboratory environments to larger-scale modules, the integration of precise interface chemistry and robust material composition is expected to play a central role in the future of high-efficiency solar energy.

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