Quantum cutting converting a ultraviolet photon into two near-infrared photons has been demonstrated by spectroscopic measurements in NaYF4:Ho3+,Yb3+ synthesized by hydrothermal method. Evidence is provided to confirm the occurrence of quantum cutting. Upon excitation of Ho3+ 5G4 level, near-infrared quantum cutting could occur through a two-step resonance energy transfer from Ho3+ to Yb3+ by cross relaxation, with a maximum quantum efficiency of 155.2%. This result reveals the possibility of violet to near-infrared quantum cutting with a quantum efficiency larger than 100% in Ho3+/Yb3+ codoped fluorides, suggesting the possible application in modifying the solar spectrum to enhance the efficiency of silicon solar cells.
Sm-doped SrBO was synthesized for high-sensitivity thermometry. A high thermal-sensitive fluorescence intensity ratio and fluorescence lifetime were achieved in a wide temperature range. At 500 K, the relative sensitivity of the temperature sensing was 2.16% K for the fluorescence intensity ratio and 3.36% K for the fluorescence lifetime. Furthermore, the fluorescence color-shifted dramatically from deep red at room temperature to green at 700 K. On the basis of this color change, a visible temperature field was obtained on quartz glass covered with our sample, which made the thermal conduction and distribution visible to the human eye. The temperature of the temperature field was determined using two methods. These outstanding properties, combined with the high sensitivity, multimode for temperature sensing and thermal stability of the sample, make SrBO:Sm a promising material for highly sensitive thermometry applications.
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