Development of efficient and stable double layer tandem solar cells

An international research team has developed efficient and stable perovskite-silicon tandem solar cells via an anion-engineering method.

Article | Spring 2021

New emerging perovskite solar cells convert light into energy, but they can be inefficient and vulnerable to the environment, degrading with, ironically, too much light along with other factors, including moisture and temperature. An international research team has developed a new type of solar cell that can withstand environmental hazards and offers 26.7% efficiency in power conversion. The researchers, led by Byungha Shin, a professor from the Department of Materials Science and Engineering at KAIST, focused on developing a new class of light-absorbing material, called a wide bandgap perovskite.

The material has a highly effective crystal structure that can process the power needs, but it can become problematic when exposed to environmental factors, such as moisture, heat, and light.

To achieve better performance, Shin and his team built a double layer solar cell, called tandem, in which two or more light absorbers are stacked together to better utilize solar energy. To use perovskite in these tandem devices, the scientists modified the material’s optical property, which allows it to absorb a wider range of solar energy. Without the adjustment, the material is not as useful in achieving high performing tandem solar cells. The modification of the optical property of perovskite, however, comes with a penalty — the material becomes extremely vulnerable to the environment, in particular, to light.

To counteract the wide bandgap perovskite’s delicate nature, the researchers engineered combinations of molecules composing a two-dimensional layer in the perovskite, stabilizing the solar cells. The development was only possible due to the engineering method, in which the mixing ratio of the molecules building the two-dimensional layer is carefully controlled. In this case, the perovskite material not only improved the efficiency of the resulting solar cell but also gained durability, retaining 80% of its initial power conversion capability even after 1,000 hours of continuous illumination. This is the first time such a high efficiency has been achieved with a wide bandgap perovskite single layer alone, according to Shin.

 

 

The researchers, having stabilized the wide bandgap perovskite material, are now focused on developing even more efficient tandem solar cells that are expected to have more than 30% power conversion efficiency, something that no one has achieved yet. These results were published in April, 2020 in Science. (Science 368.6487 (2020): 155-160)