Fig. 3: UV light-excited multiexcitonic emissions

a Contour plot of the excitation-wavelength-resolved PL spectra of Cs₂NaScCl₆:Sb³⁺ (0.75%) crystal highlighting its dual-excitonic emissions. Note that the blue emission dominated over the yellow one except under 302 nm excitation. b PLE (dotted lines) and PL (solid lines) spectra of Cs₂NaScCl₆:Sb³⁺crystal, and insets show the optical images of single crystals under UV excitation at 302 and 335 nm. Scale bar = 1 mm. c Time-resolved PL mapping and steady-state PL spectrum under 302 nm excitation, along with the calculated average lifetimes versus the emission wavelengths. d The plot of FWHM of blue and yellow emissions versus the temperature. By fitting the experimental data, the parameters were derived to ℏω_op = 36.27 meV, S = 15.97, γ_op = 295.07 meV for blue emission and ℏω_op = 14.78 meV, S = 60.53, γ_op = 172.61 meV for yellow one, respectively. e The integral intensity of Cs₂NaScCl₆ and Cs₂NaScCl₆:Sb³⁺ (0.02%) crystals under 335 nm excitation as a function of Sb³⁺ content detected by ICP-MS analysis, and the insets show the corresponding PL spectra. Note that (1–4) represented bare Cs₂NaScCl₆ prepared using ScCl₃·6H₂O-Aladdin, ScC₆H₉O₆·xH₂O-Aladdin, Sc₂O₃-Aladdin, or Sc₂O₃-Alfa Aesar, while (5) represented Cs₂NaScCl₆:Sb³⁺ (0.02%) crystal. f The calculated electronic structure of bare and Sb³⁺-doped Cs₂NaScCl₆ crystals. g The schematic energy level diagram showing the excitation and STE emission processes