Japan’s PXP Co., Ltd. and Tokyo Gas Co., Ltd. are developing film-type solar cells under a project selected by Kanagawa Prefecture.The initiative is part of the Reiwa Carbon Neutrality R&D program. It targets industrial rooftops with low load-bearing capacity, such as slate roofs. These cells use chalcophylite material and weigh just 1kg/m². This is Japan’s first attempt to install such cells on lightweight rooftops. The companies aim to commercialize the solution by the end of FY2026. They are working to establish panel structures and construction methods. Durability and safety are verified through demonstration installations. The project addresses limited land availability and structural constraints in solar deployment. Japan’s potential rooftop capacity on such buildings is estimated at 169 GW by 2050. That figure is more than twice the nation’s current installed solar capacity.