Researchers from Australia's Monash University, The Australian National University (ANU), Flinders University, The University of Sydney and Germany's Karlsruhe Institute of Technology have achieved a 30.3% efficiency with a perovskite and silicon tandem solar cell.
The team developed the highly efficient tandem cell, while also enhancing its operational stability. Their work builds on a previous record set by ANU researchers in 2020, and was funded by the Australian Renewable Energy Agency (ARENA).
Methylammonium (MA)-free perovskite solar cells have the potential for better thermal stability than their MA-containing counterparts. However, the efficiency of MA-free perovskite solar cells lags behind due to inferior bulk quality. In their recent work, the team added 4-methylphenethylammonium chloride (4M-PEACl) into a MA-free perovskite precursor, which results in greatly enhanced bulk quality.
The perovskite crystal grains were significantly enlarged, and defects were suppressed by a factor of four upon the incorporation of an optimal concentration of 4M-PEACl.
Quasi-2D perovskites were formed and passivated defects at the grain boundaries of the perovskite crystals. Furthermore, the perovskite surface chemistry was modified, resulting in surface energies more favorable for hole extraction.
This novel approach led to a steady state efficiency of 23.7% (24.2% in reverse scan, 23.0% in forward scan) for MA-free perovskite solar cells. The devices also showed excellent light stability, retaining more than 93% of the initial efficiency after 1000 h of constant illumination in a nitrogen environment.
In addition, a four-terminal mechanically stacked perovskite-silicon tandem solar cell with champion efficiency of 30.3% was obtained using this MA-free composition. The encapsulated tandem devices showed excellent operational stability, retaining more than 98% of the initial performance after 42 day/night cycles in an ambient atmosphere.
Researcher The Duong said: “With these tandem solar cells, the perovskite top cell can efficiently absorb the blue light and transmit the red light to the silicon bottom cell, producing significantly more energy from sunlight than each individual device”.
“Surpassing the 30% mark is significant,” said Duong. “That’s currently considered the efficiency threshold for the commercialization of tandem technology like that used in our study. The current predictions are that tandem solar technology will be in mass production by 2026. However, more work is still needed to upscale and ensure the technology can be stable in the field over 25 to 30 years.”
The ANU team is now working to improve the efficiency and stability of the solar cells.