fig4

Figure 4. (A) Normalized intensities of UC emissions centered at 525, 545, and 656 nm for the CZF-Li-38 NCs as a function of temperature. Fitting curves of temperature-dependent (B) LIR(I₅₂₅/I₅₄₅) and (C) LIR(I₆₅₆/I₅₂₅). Comparison of (D) relative (S_r) and (E) absolute (S_a) sensitivities of the CZF-Li-0, CZF-Li-35, and CZF-Li-38 NCs based on the TCLs-LIR method. Comparison of (F) S_r and (G) S_a of the CZF-Li-0, CZF-Li-35, and CZF-Li-38 NCs based on the NTCLs-LIR method; (H) Temperature uncertainty for the CZF-Li-38 NCs at different temperatures based on the TCLs- and NTCLs-LIR methods; (I) Thermal cycling measurements for the LIR(I₅₂₅/I₅₄₅) and LIR(I₆₅₆/I₅₂₅) of the CZF-Li-38 NCs between 303 and 483 K. UC: Upconversion; CZF-Li-X NCs: Cs₂ZrF₆:Yb/Er NCs with and without Li⁺-doping; NCs: nanocrystals; TCLs: thermally coupled levels; LIR: luminescence intensity ratio; NTCLs: non-thermally coupled levels.