Figure 2: Excitation fluence dependence of multiphoton-excited upconversion PL(slopes) and action cross-sections as a function of excitation wavelengths. | Nature Communications

Figure 2: Excitation fluence dependence of multiphoton-excited upconversion PL(slopes) and action cross-sections as a function of excitation wavelengths.

From: Giant five-photon absorption from multidimensional core-shell halide perovskite colloidal nanocrystals

Figure 2

(a) Slopes n plotted as a function of laser excitation wavelength (photon energy), where n is defined as the excitation fluence dependence of the MPPL signal that is proportional to (excitation fluence)n. (b) Two-photon action cross-section (ησ2) spectra of the MAPbBr3, MAPbBr3/(OA)2PbBr4 and CsPbBr3 NCs in the wavelength range 675–1,000 nm. (c) Three-photon action cross-section (ησ3) spectra of the perovskite NCs in the range 1,050–1,500 nm. (d) Four-photon action cross-section (ησ4) spectra of the perovskite NCs in the range 1,550–2,000 nm. Insets in (b–d) show the corresponding spectral dependence of MPA cross-sections (σn) of the perovskite NCs. Error bars indicate the experimental uncertainty of ±15%.

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