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Korea Institute of Energy Research develops perovskite–CIGS tandem solar cell
The next-generation perovskite/copper indium gallium selenide (CIGS) solar cell developed by the Korea Institute of Energy Research (KIER) has achieved an energy conversion efficiency of 26.7%, breaking the world record for the highest certified efficiency. This achievement follows last year’s result by a joint team from Seoul National University and the Korea Institute of Science and Technology (KIST), which set the previous world-best efficiency at 26.3%, and once again a Korean research team has set a new global benchmark.
KIER announced on the 1st that the power conversion efficiency record of its perovskite/CIGS tandem solar cell, developed by the Photovoltaics Research Center, has been officially certified by the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) in Germany and listed as the world’s highest record in the solar cell efficiency tables by type published by the National Renewable Energy Laboratory (NREL) in the United States.
The most widely used silicon solar cells today have a theoretical maximum efficiency of about 29%, which means there is a limit to further improvements when relying on a single material. This is why tandem solar cells, which stack solar cells with different characteristics in multiple layers to utilize a broader range of sunlight, are attracting attention.
In the perovskite/CIGS tandem solar cell developed by KIER, a perovskite solar cell is placed on the top and a CIGS solar cell on the bottom. This structure divides and absorbs sunlight in different wavelength ranges to maximize power generation efficiency. However, during the process of combining the two solar cells, the perovskite light-absorbing layer tends to degrade and absorb unnecessary light, which leads to performance losses and has been a major challenge.
The research team developed interfacial layer materials and processing technologies that can reduce damage to the perovskite, and optimized the structure of the top transparent electrode and charge transport layers to cut unnecessary light absorption and minimize photogenerated current losses. As a result, they achieved a 27% efficiency under laboratory conditions and obtained certification from Fraunhofer ISE for an official efficiency of 26.7%.
Perovskite/CIGS tandem solar cells can be fabricated in a lightweight, flexible thin-film structure, which makes them highly promising as power sources not only for buildings and vehicles but also for small satellites and space data centers, where weight and installation area are critical. For example, if the solar panels are rolled up and launched into space, the available payload volume of the launch vehicle can be maximized.
Jung In-young, senior researcher at KIER who led the study, said, “We simultaneously reduced interfacial and optical losses that occur during the process of integrating perovskite and CIGS, thereby improving both efficiency and stability,” adding, “Having our efficiency verified by a world-class certification body and listed as the top efficiency is an objective recognition of the competitiveness of our technology.”
