Dual Minimization of Spectrum Overlap for High-Sensitivity, High-Temperature Sensing

Minimizing the spectrum overlaps of energy transfer (ET) is necessary but not sufficient for achieving high-sensitivity film thermosensing. Herein we have designed two blue emitters of DBA-BPAc and Z-DBABH exhibiting blue and bluish-green emissions, respectively, to hybridize with the red-emitting Ir(MDQ)₂(acac). Compared with Z-DBABH, DBA-BPAc shows a larger spectrum overlap of ET and a relatively smaller discrepancy in fluorescence thermal decay, while its emission spectrum displays a much smaller overlap with that of Ir(MDQ)₂(acac). The dual minimization of spectrum overlap of ET and emissions results in its superior ratiometric film thermosensing of the DBA-BPAc film in wide-range and high-temperature regions. The DBA-BPAc/Ir(MDQ)₂(acac) film exhibits a maximum relative sensitivity (S_r) of 3.36% °C^-1 at 166 °C, exceeding 0.43% °C^-1 in 50-265 °C. In comparison, the Z-DBABH/Ir(MDQ)₂(acac) system displays a reliable but relatively lower performance, with a maximum S_r of 1.92% °C^-1 (at 300 °C). The temperature resolution remains below 2.06 °C throughout the entire temperature range (20-300 °C), achieving a best value of 0.60 °C at 180 °C. Notably, both films display distinct naked-eye color transitions with temperature changes, enabling multi-level anti-counterfeiting applications. This work provides new insights for designing high-performance thermometers.