Figure 2. Properties of an exemplary sample for anti-stokes non-coherent fluorescence probing.

(a) Photograph of an as-prepared disc sample. Scale bar indicate a size of 4 mm. (b) Time-dependent electron spin resonance spectra of the sample after charging. (c) Temperature-dependent photocurrent excitation spectra for the range of 20 ~ 300 K. (d) Luminescence image taken at the interval of 24 hours after charging of the sample for illumination with an incoherent LED operating at a wavelength of 800 nm (here: 7.87 mW/cm²). (e) Static photoluminescence spectrum under excitation at 800 nm and (f) the corresponding photoluminescence excitation spectra monitored at 700 nm of the charged sample. Before measurements, effective optical charging of the probe can be done by UV-vis light for 5 min, the measurements were taken at the interval of 24 hours after charging.