Fig. 1. Volatile ammonium-driven phase reconstruction.

Fig. 2. Mechanism illustration of the phase reconstruction process. In situ PL spectra of w/PEAAc (a), w/PEABr (b), and pristine CsPbBr3 films (c), as well as time-dependent UV spectra of w/PEAAc (d), w/PEABr (e), and pristine CsPbBr3 films (f), focusing on the initial 90 s of thermal annealing. (g) XPS core-level spectra of Pb 4f. H1 NMR spectra of w/PEAAc and w/PEABr before annealing (h) and after annealing (i).

Fig. 3. Recombination dynamics for w/PEAAc films and w/PEABr films. Temperature-dependent PL spectra of w/PEAAc films (a) and w/PEABr films (b). Inset: variation of the integrated intensity with the reciprocal of temperature. The Eb values can be described by the expression of I(T)=I0/(1+aT3/2e−Eb/kT), where T is the temperature and k is the Boltzmann constant. (c) Film’s PLQY as a function of carrier density for w/PEAAc films and w/PEABr films, respectively. Bleaching kinetics with different pump densities for w/PEAAc films (d) and w/PEABr films (e). (f) Auger recombination lifetimes extracted from TA spectra of w/PEAAc and w/PEABr films at ∼4.9μJcm−2.

Fig. 4. ASE characterizations of the perovskite thin films. (a) Pump fluence-dependent PL spectra of w/PEAAc films under fs-pumping (400 nm, 200 fs, 1 kHz). Inset: ASE integrated intensity and FWHM as a function of pump fluence. (b) Streak camera images showing time-resolved PL emission under the excitation fluence of below (top) and above (bottom) the ASE threshold. (c) Variation of the ASE intensity with stripe length at different pump fluences. (d) Pump fluence-dependent PL spectra of w/PEAAc films under ns-pumping (355 nm, 1.3 ns, 100 Hz). Inset: ASE integrated intensity and FWHM as a function of pump fluence. (e) Evolution of ASE intensity under continuous irradiation of ns-pumping. (f) ASE threshold for w/PEAAc and w/PEABr films under ns-pumping and fs-pumping. (g) Comparison of carrier decay curves extracted from TA spectra and a laser pulse duration of 1 ns. (h) Schematic diagram of rapid Auger recombination hindering carrier accumulation. (i) Tunable ASE over a broad visible light spectrum by halide compositional modulation.

Fig. 5. Single-mode vertical cavity surface-emitting laser. (a) Schematic of the vertical cavity surface-emitting laser. (b) Evolution of PL spectra under various pump fluences under quasi-continuous ns-pumping. Inset: far-field pattern of the lasing. (c) Integrated intensity as a function of pump fluence. Inset: lasing spectrum with a narrow FWHM of 0.14 nm, indicating a Q factor of 3850. (d) Comparison of lasing thresholds and quality factors of perovskite lasers under ns-pumping.^{20,33,56–63}" target="_self" style="display: inline;">^–63