Ultraviolet to near-infrared downconversion in Yb3+–Na+ codoped Sr2CaWO6

• Yb3+–Na+ codoped Sr2CaWO6 powders were prepared by solid-state reaction.
• The phosphor possesses a broadband absorption in the UV region.
• Ultravoilet to near-infrared downconversion was observed.
• Theoretical quantum efficiency can reaches up to 190%.
• The phosphor is a promising quantum-cutting material for its application in solar cells.

This study investigated photoluminescent properties of Sr2CaWO6:Yb3+, Na+ phosphor. The samples were successfully synthesized via a solid-state reaction method with various doping concentrations. The phosphor can efficiently absorb ultraviolet photons of 250–350 nm and transfer its absorbed photon energy to Yb3+ ions. Then subsequent quantum cutting between WO6 groups and Yb3+ ions takes place, down-converting an absorbed ultraviolet photon into two photons of 1007 nm radiations. Analyses of decay curves of different samples reveal an efficient energy transfer from WO6 groups to Yb3+ ions. Cooperative energy transfer from host to Yb3+ ions is responsible for downconversion via lifetime analysis. Quantum efficiencies were calculated, and estimated maximum efficiency reached 190%. These phosphors combine wide wavelength absorption in the ultraviolet range with high quantum efficiency, enabling potential application of efficiency enhancement of Si solar cell.