Upconversion materials: A new frontier in solar water-splitting‎

Solar water splitting is one of the most direct ways to produce green hydrogen using sunlight. However, most photocatalysts and photoelectrodes absorb only a limited portion of solar radiation, mainly ultraviolet and part of the visible spectrum. A large share of solar energy, particularly infrared photons, remains unused. This spectral mismatch significantly limits the efficiency of hydrogen production from sunlight.