Testing nanocrystalline CdWO4 doped with Yb3+ as a possible down-conversion phosphor

• CdWO4:Yb3+ nanophosphors were synthesized by microwave-hydrothermal method.
• Efficient conversion of absorbed UV photons into Yb3+ IR fluorescence was detected.
• Excitonic PL quenching kinetics is compared with the model of cooperative quenching.
• The quenching kinetics contradicts the existence of cooperative down-conversion.

The CdWO4:Yb3+ (0.1, 2, 3%) nanophosphors have been synthesized using microwave-hydrothermal treatment. The spectral and kinetic characteristics of their luminescence were studied with the aim to check the possibility of cooperative energy transfer from CdWO4 self-trapped excitons to Yb3+ pairs, which can provide down-conversion of UV photons absorbed by the CdWO4 host into two lower-energy (IR) photons emitted by two Yb3+ ions. The obtained results have shown the conversion of absorbed UV photons into Yb3+ IR fluorescence. However, the obtained parameters of decay kinetics of both intrinsic luminescence of CdWO4 and IR fluorescence of Yb3+ did not confirm the existence of cooperative energy transfer from STE to two Yb3+ ions in the studied CdWO4:Yb3+ nanophosphors. The reason is supposed to be rather low concentrations of Yb3+ obtained in the synthesized samples which prevents the creation of high enough concentration of Yb3+ pairs with short distances between the ions.