Highest power conversion rate for copper gallium solar cell achieved

Researchers at Japan’s National Institute of Advanced Industrial Science & Technology (AIST) have achieved a new power conversion efficiency record of 12.28% for copper gallium selenide (CuGaSe₂) solar cells. CuGaSe₂ is an indium-free, wide-bandgap chalcopyrite semiconductor with a direct bandgap of about 1.68 eV, making it highly effective at absorbing visible sunlight. This efficiency surpasses previous records for wide-bandgap chalcogenide solar cells in the 1.65–1.75 eV range, particularly for indium-free chalcopyrite or CIGS-related devices, as independently verified by AIST’s Photovoltaic Calibration, Standards and Measurement Team. The improved performance stems from a refined three-stage fabrication process where aluminum and rubidium fluoride are introduced to enhance the open-circuit voltage and reduce charge carrier recombination. The device structure includes a soda-lime glass substrate with a molybdenum back contact,