A University of Sydney-led team has set a record for solar technology, creating the largest and most efficient triple-junction perovskite-perovskite-silicon tandem solar cell reported.
Led by Professor Anita Ho-Baillie, John Hooke Chair of Nanoscience at the University of Sydney Nano Institute and School of Physics, the result demonstrates high efficiency and durability, important steps for overcoming barriers to the development of perovskite tandem solar cell technology.
The team’s 16cm2 triple-junction cell achieved an independently certified steady-state power conversion efficiency of 23.3%—the highest reported for a large-area device of this kind. At the smaller scale, a 1cm2 cell recorded 27.06% efficiency and set new standards for thermal stability.
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The results are published in the Nature Nanotechnology.
In a global first, the 1cm2 cell passed the International Electrotechnical Commission’s (IEC) Thermal Cycling test, which exposes devices to 200 cycles of extreme temperature swings between -40 and 85 degrees. This cell retained 95% of its efficiency after more than 400 hours of continuous operation under light.
A triple-junction solar cell uses three interconnected semiconductors, each absorbing a different part of the solar spectrum to maximise conversion of the sun’s energy into electricity.
Professor Ho-Baillie said this latest advance 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.”
The researchers replaced less stable methylammonium, commonly used in high-efficiency perovskite cells, with rubidium creating a perovskite lattice that is less prone to defects and degradation. They also replaced the less stable lithium fluoride with piperazinium dichloride for a new surface treatment.
To connect the two perovskite junctions, the researchers used gold at the nanoscale and, using advanced transmission electron microscopy, clarified that gold at this scale is in the form of nanoparticles, not as a continuous film as many perceived. The team used this knowledge to engineer gold nanoparticle coverage to maximise the flow of electric charge and light absorption by the solar cell.
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These developments enabled the triple-junction cell to sustain high efficiencies over more time and under stress.
Perovskites are an emerging class of photovoltaic materials valued for their low-cost manufacturing and ability to capture more of the solar spectrum when stacked in multiple layers with silicon. Until now, however, scaling devices beyond the laboratory and ensuring their stability under real-world conditions have been major challenges.
The research was carried out in collaboration with international partners from China, Germany and Slovenia, with support from the Australian Renewable Energy Agency (ARENA) and the Australian Research Council.
