Researchers at Kyushu University have developed a groundbreaking solid-state material capable of converting ordinary visible sunlight into higher-energy ultraviolet (UV) light. The discovery could pave the way for cleaner, more efficient technologies powered entirely by natural sunlight. The process, known as photon upconversion, combines the energy of two visible-light photons to create a single UV photon. While scientists have understood the concept for years, making it wor