Abstract: Due to the better matched with the spectral response of silicon-based photodetectors，offering a promising route toward compact，highly sensitive radiation detection，the near infrared scintillators have attracted much interest. The Sm²⁺ activated halide scintillators with emission wavelength of 700 nm to 900 nm have been developed. However，the strategy of single Sm²⁺ doping have some disadvantage of low light out and worse energy resolution. Usually，the co-doping is an effect method to improve the scintillation properties by adjusting the energy transfer efficiency，defect structure and quantity.In this work，the Cs₂LiLaBr₆∶Ce³⁺ with excellent scintillation properties is chosen as a host，and the Sm²⁺ is introduced as a near infrared emitting center to construct an energy transfer route from Ce³⁺ to Sm²⁺. Cs₂LiLaBr₆∶Ce³⁺，Sm²⁺ single crystals with varied Sm²⁺ concentrations were successfully grown by the vertical Bridgman method. The axial distribution and segregation behavior of Sm²⁺ were quantitatively evaluated using ICP-MS，yielding an effective segregation coefficient of about 2.0，which indicates a pronounced tendency of Sm enrichment during crystal growth. Optical properties and energy transfer were investigated by steady state photoluminescence，time resolved decay measurements，and photoluminescence quantum yield. In addition，X-ray excited luminescence and thermoluminescence were employed to probe defect related trapping and radiative processes.The co-doped crystals exhibit three characteristic emission bands centered at approximately 390，420 and 770 nm. The two visible bands originate from Ce³⁺ 5d to 4f transitions，while the near infrared band is assigned to Sm²⁺ 5d-4f emission，demonstrating successful introduction of near infrared luminescence for the Cs₂LiLaBr₆ matrix. The spectral overlap between Ce³⁺ emission and Sm²⁺ excitation is observed，together with the evolution of decay dynamics，provide strong evidence for energy transfer from Ce³⁺ to Sm²⁺. Notably，a number of energies are loss during the energy transfer pathway of Ce-Sm，implying the presence of competing nonradiative channels and trap assisted dissipation. The photoluminescence quantum yield increased firstly and then decreased as Sm²⁺ concentration raised. It reaches a maximum value of about 98.5% when the Sm²⁺ concentration is 3%. The concentration quenching is happened for the higher doping concentration. Thermoluminescence and X-ray excited luminescence further reveal that the Sm²⁺ co-doping reconstructs the defect energy of the host，altering the trap depth and recombination pathways.Overall，this study establishes a systematic design and characterization framework for Ce³⁺ sensitized Sm²⁺ near infrared emission in the Cs₂LiLaBr₆ host，provides quantitative insight into dopant segregation，and clarifies the coupled roles of energy transfer losses and defect evolution. These findings offer practical guidance for optimizing near infrared halide scintillators intended for silicon-based readout and advanced radiation detection applications.

Key words: Sm²⁺ doping; Cs₂LiLaBr₆∶Ce³⁺; Sm²⁺; vertical Bridgman method; energy transfer; scintillation crystal; luminescence property