Quantum cutting is a promising approach to enhance the efficiency of silicon solar cells.The Yb³⁺ is chosen as the acceptor ion since it has been extensively used for its near-infrared emission around 980 nm (²F_5/2→²F_7/2), which is just above the bandgap of Si-based solar cells.The efficiency of quantum cutting mechanism via two-step energy transfer from Tm³⁺ to Yb³⁺ is investigated in Tm³⁺/Yb³⁺ co-doped NaLu(WO₄)₂ phosphors. Tm³⁺-doped and Tm³⁺/Yb³⁺ co-doped NaLu(WO₄)₂ phosphors were prepared by a high temperature solid-state reaction method. The crystal structure of the samples was analyzed by X-ray Diffraction (XRD). X-ray diffraction shows that all of samples are pure tetragonal-phased NaLu(WO₄)₂ powders. It is known that the high doping concentration will result in the concentration quenching which further depresses the quantum cutting efficiency.Through the dependences of emission intensities for all transitions of Tm³⁺ ,it can indicated that the population of the metastable levels reaches its maximum at around 1 mol%. To achieve effective quantum cutting, the optimum concentration of Tm³⁺ was determined to be 1 mol% through optical spectral measurements. By analyzing the spectra and luminescence decays of Tm³⁺/Yb³⁺ co-doped samples, it was confirmed that Tm³⁺-sensitized-Yb³⁺ quantum cutting is achieved via two-step energy transfer processes, namely, the first energy transfer ¹G₄(Tm)+²F_7/2(Yb)→³H₄(Tm)+²F_5/2(Yb) results in the emission of a 980 nm photon from Yb³⁺, and the second energy transfer ³H₄(Tm)+²F_7/2(Yb)→³H₆(Tm)+²F_5/2(Yb) results in the emission of another 980 nm photon from Yb³⁺. The luminescence lifetime decay curve of Tm³⁺ with different Yb³⁺ concentrations is gradually shortened with the increase of Yb³⁺ ions concentration, which indicates energy transfer efficiency and quantum efficiency can be improved with the increase of Yb³⁺ ions concentration.The quantum cutting efficiencies of Tm³⁺/Yb³⁺ co-doped NaLu(WO₄)₂ phosphors were calculated using fluorescence lifetimes of corresponding levels of Tm³⁺ and Yb³⁺.The Yb³⁺ concentration dependent energy transfer efficiency from Tm³⁺ to Yb³⁺ has also been evaluated. The results indicate that the quantum cutting efficiencies are relatively low that is because the energy transfer efficiencies are low. The low energy transfer efficiencies are caused by the large energy mismatch in the two-step energy transfers. Meanwhile, it was also found that the back energy transfer from Yb³⁺ to Tm³⁺, viz, ³H₆(Tm)+²F_5/2(Yb) →³H₅(Tm)+²F_7/2(Yb), displays bad influence to the quantum cutting and depresses quantum cutting efficiency of Tm³⁺/Yb³⁺ co-doped materials.The results further complements the theory of quantum cutting that convert one blue photon to two near-infrared photons. This material indicate the potential application in improving the photoelectric conversion efficiency of the silicon based solar cells.