Korean Researchers Achieve 26.7% Efficiency in Solar Cell

Researchers at the Korea Institute of Energy Research (KIER) have reached a new milestone in solar technology, developing a tandem solar cell with a verified power conversion efficiency of 26.7%. The Fraunhofer Institute for Solar Energy Systems in Germany confirmed the result, which has now been added to the Best Research-Cell Efficiency Chart maintained by the US Department of Energy’s National Laboratory of the Rookies. This tandem cell pairs a perovskite top layer with a copper indium gallium selenide (CIGS) bottom layer, and the record-setting performance applies to devices smaller than 1 cm². Beyond the efficiency gain, the design points toward a future for solar solutions that are both lightweight and flexible.

This progress builds on the steady evolution of perovskite materials, which are valued for their high efficiency and relatively low production costs. Because both the perovskite and the CIGS layers can be fabricated as thin films, they are ideal candidates for flexible solar panels. However, combining the two materials is difficult; researchers often struggle with the degradation of the perovskite layer and unwanted light absorption. By finding ways around these technical hurdles, the KIER team has improved the overall stability of the cells alongside their performance.

Reaching this level of efficiency required a detailed redesign of interface materials and processing techniques, specifically to prevent damage to the perovskite during assembly. The team also refined the top transparent electrode and the charge transport layer to minimize light loss. Lead researcher In-Young Jeong noted the importance of these adjustments, stating that the work "not only improves efficiency but also stability by mitigating losses that occur when integrating perovskite with CIGS solar cells." The project reflects a broader collaborative effort at KIER to push the boundaries of renewable energy.

The implications of this work go beyond laboratory metrics. More efficient cells can lower the overall cost of solar power, making it more practical for large-scale adoption. From an environmental perspective, higher efficiency allows for more electricity to be generated from the same surface area, which could help reduce the amount of land needed for solar farms. On a social level, the possibility of lightweight, flexible panels could make renewable energy more accessible for portable electronics and mobile applications.

The KIER team is already looking toward the next milestone. In-house testing has reached efficiencies as high as 27.5%, suggesting that this latest record is a stepping stone rather than a ceiling. This progress helps make solar technology more competitive globally as the world shifts toward sustainable energy. As the demand for clean power continues to rise, technical refinements like these will be central to how energy is produced in the coming years.