Cooperative down-conversion and near-infrared luminescence of Tb3+–Yb3+ co-doped CaMoO4 broadband phosphor

An efficient near-infrared (NIR) quantum cutting (QC) CaMoO4:Tb3+, Yb3+ phosphor promising for silicon solar cells was successfully prepared using combustion method. Upon the excitation at 306 nm, a green visible photon is emitted by Tb3+, while two NIR photons are emitted by Yb3+ through cooperative energy transfer (CET) from one Tb3+ ion to two Yb3+ ions. Visible to NIR emission, decay lifetimes of Tb3+, and quantum efficiency (QE) are studied for samples with various Yb3+ concentration. It has been found that the luminescence intensity at around 997 nm from Yb3+ increases, however, it decreases at a high Yb3+ co-doping content of 10% due to concentration quenching, while the emission and lifetime of Tb3+ decreases monotonically as compared to that of Tb3+ doped CaMoO4. The maximum energy transfer efficiency (ETE) and the corresponding down-conversion (DC) QE are estimated to be 60.4% and 160.4%, respectively.