Fig. 1. (Color online) The structure and morphology characterization of ultrathin CsPbCl₃ nanowires (NWs) epitaxial on mica. (a) Scanning electron microscopy (SEM) image of the ultrathin CsPbCl₃ NWs grown on (001)-mica by chemical vapor deposition method. (b) Atomic force microscopy (AFM) image of the CsPbCl₃ NWs, scale bar: 100 nm. (c) Corresponding data of CsPbCl₃ NWs height extracted from (b). (d) X-ray diffraction pattern of the CsPbCl₃ NWs on mica (red line) and mica (black line).

Fig. 2. (Color online) Photoluminescence (PL) emission spectra of thin (height: ~ 7 nm; upper panel) and thick (height: ~ 8 μm; lower panel) CsPbCl₃ NWs on mica at (a) 294 K and (b) 78 K, respectively. Solid and dashed lines: Lorentzian function fitting curves; open circles: experimental data. The excitation power density P_ex of ~ 1.2 kW/cm².

Fig. 3. (Color online) (a) Power-dependent emission spectra of thin CsPbCl₃ NWs on mica at 294 K with P_ex from ~ 0.3 to 61.1 kW/cm². Scatters: experimental data points; red and blue dot lines are the fitting curves of the FX and X-band emission by Lorentzian function, respectively. (b) Integrated PL intensity as a function of P_ex extracted from (a). Red scatters and blue scatters: integrated PL peak intensity of FX and X-band as a function of P_ex, respectively; black scatters: the integrated PL intensity of NWs; solid lines: fitting curves.

Fig. 4. (Color online) (a) Temperature-dependent PL spectra of CsPbCl₃ NWs on mica in the range of 294 − 78 K. The red and blue dot lines are the fitting curves of the FX and X-band by Lorentzian function, respectively. Scatters: experimental data point; P_ex: ~ 1.2 kW/cm². (b) Corresponding integrated PL intensity (blue scatters) and center peak energy (pink scatters) of FX as a function of temperature (solid red line, fitting curve). (c) FWHM of FX emission peak (blue scatters, experimental data points; red line, fitting curve). The Γ_in, Γ_AC and Γ_OC represent the contribution of inhomogeneous broadening, acoustic phonon and optical phonon for FWHM broaden. Solid line, Γ_in + Γ_AC + Γ_OC; dashed dot line, Γ_in + Γ_OC; dot line, Γ_in + Γ_AC. The fitting result show that the temperature-dependent FWHM broaden is mainly contributed from the optical phonon.