Reversing the temperature dependence of the sensitized luminescence intensity
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(a) Luminescence spectra for in an amorphous film (, blue curves) and for a nanocrystalline one (, red curves). The inset shows the decay curves for amorphous SiO (, blue curves) and for NCs (, red curves), clearly showing difference in the dynamics for the amorphous SRO vs nanocrystalline films. The dark blue and dark red curves are samples doped with Er. Representative TEM images for the same undoped SiO samples are also shown, indicating the amorphous vs nanocrystalline nature of the films. The scale bar is 5 nm. (b) Blue curves show the spectra for an amorphous (defect) sensitizer at temperatures of 77 and 300 K; red curves are for the NC sensitizer. Notice the opposite trend as a function of . (c) shows the luminescence spectrum for SiO:Er , fit with a set of Gaussians corresponding to radiative transitions between the and energy levels in an amorphous host (Ref. 27). The fit is sufficiently good that the data points cannot be seen under the black fitted curve.
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(a) integrated luminescence intensity as a function of for several -SRO sensitizers. The inset shows SRO intensities for (orange line) and (blue line), also as a function of . (b) is the same as in (a) except that the sensitizer was nanocrystalline. The inset in (b) shows a model for NC sensitizers (left) and amorphous sensitizers (right), which can explain the trends shown in the main panel. Lines are fit with a logarithmic function as guides to the eye. One data point (filled circle, instead of open) was not fit since it appeared to be an outlier.
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