Fig. 1. Crystal structure and thin film preparation process of CsPbBr3.

Fig. 2. X-ray diffraction patterns of CsPbBr3 nanocrystals.

Fig. 3. (a) TEM characterization of CsPbBr3 nanocrystals. (b) The size distribution of the nanocrystals. (c)–(g) Scanning electron microscopy (SEM) characterization of CsPbBr3 perovskite thin films with thicknesses of 300, 450, 800, 1800, and 4500 nm.

Fig. 4. Schematic diagram of electron beam pumping source.

Fig. 5. Photoluminescence spectra of CsPbBr3 quantum dot thin films.

Fig. 6. Electron beam pumping spectra of CsPbBr3 quantum dot thin films by different acceleration voltages.

Fig. 7. Luminescence intensity of CsPbBr3 quantum dots with different film thicknesses pumped by an electron beam. The inset shows the lasing threshold and FWHM variation of the 300 nm CsPbBr3 quantum dot film.

Fig. 8. Schematic diagram of random lasing mechanism of electron beam pumped CsPbBr3 quantum dots.

Fig. 9. Energy distribution of the electron beam inside the quantum dot films.