A team led by researchers from the University of Sydney has claimed it created the largest and most efficient triple-junction perovskite-perovskite-silicon tandem solar cell reported.

The research team’s 16 cm² triple-junction cell achieved a 23.3% steady-state power conversion efficiency, which is the highest reported level for a large area of its kind. This efficiency level was certified independently.

The research, titled “Tailoring nanoscale interfaces for perovskite–perovskite–silicon triple-junction solar cells,” was published in Nature Nanotechnology.  It was conducted in collaboration with partners from China, Germany, and Slovenia. It also received support from the Australian Renewable Energy Agency and the Australian Research Council.

The report stated that the research’s result demonstrates high efficiency and durability. These are important steps to overcome barriers to perovskite tandem solar cell technology development.

A smaller 1 cm² cell recorded 27.06% efficiency, which the team said is a new standard for thermal stability.

The 1 cm² cell passed the International Electrotechnical Commission’s thermal cycling test. Under this test, devices were exposed to 200 cycles of extreme temperature swings ranging from -40^o to 85^o. During testing, the research team’s cell retained 95% efficiency after over 400 hours of continuous operation under light.

A triple-junction solar cell utilizes three interconnected semiconductors, with each absorbing a different part of the solar spectrum. The research team said this maximizes the conversion of solar energy into electricity.

Methodology

Anita Ho-Baillie, John Hooke Chair of Nanoscience at the University of Sydney, said the result was achieved by re-engineering the chemistry of the perovskite material and the triple junction cell design.

“We improved both the performance and the resilience of these solar cells,” she said. “This not only demonstrates that large, stable perovskite devices are possible but also shows the enormous potential for further efficiency gains.”

Researchers said they replaced the less stable methylammonium in the solar cell, which is used in high-efficiency perovskite cells, with rubidium. This created a perovskite lattice that is less susceptible to degradation and defects. The team also replaced the less stable lithium fluoride with piperazinium dichloride for a new surface treatment.

The researchers also utilized gold at the nanoscale to connect the two perovskite junctions, implementing advanced transmission electron microscopy. The gold is in the form of nanoparticles at this scale and not a continuous film

Using this knowledge, the team engineered the gold nanoparticle coverage to maximize the flow of electric charge and the solar cell’s light absorption.

Such developments enable the triple-junction cell to sustain high efficiencies under stress and over longer periods.

Solar Energy Future

The report stated that perovskites are valued for their low-cost manufacturing and the ability to capture a greater part of the solar spectrum when stacked with silicon in multiple layers. However, until now, scaling devices beyond the laboratory and ensuring their stability in real-world conditions have posed considerable challenges.

Ho-Baillie said the research’s result is the largest triple-junction perovskite device demonstrated to date. It has also been tested rigorously and certified by independent laboratories. “That gives us further confidence that the technology can be scaled for practical use.”

A U.S. Department of Energy-funded study by the University of Utah revealed the potential of phase-transitioned hybrid perovskites for use in solar cell manufacturing. The study was published under the research paper titled “Coupled optical and structural properties of two-dimensional metal-halide perovskites across phase transitions” in the journal Matter.

In May this year, a study by the U.S. National Renewable Energy Laboratory claimed it improved perovskite solar cell technology performance by replacing the commonly used fullerene electron transport layer with a newly synthesized ionic salt, commonly referred to as CPMAC.