Size-Dependent Lasing Emission and Carrier Dynamics in CsPbBr ₃ Crystals across Subwavelength to Micrometer Scales

The size-dependent lasing behavior and carrier dynamics of CsPbBr3 perovskite micro/nanostructures remain inadequately explored, particularly across the critical subwavelength to micrometer scale range. Herein, we systematically investigate the lasing performance and recombination pathways of CsPbBr3 nanowires/microwires (NWs/MWs) and nanoplatelets/microplates (NPs/MPs) with sizes spanning 0.25–12.7 μm. As the crystal size increases, the lasing emission wavelength exhibits a significant red shift, governed primarily by cavity-mode resonance rather than quantum confinement. A unified quantitative model is developed to correlate the lasing wavelength with crystal size, incorporating effective refractive index variations and mode competition effects. The recombination mechanism converts from trap-assisted recombination to bimolecular and Auger recombination with an increase in pump fluence. The competitive recombination pathways of excitons and free charge carriers evolve dynamically with size. Experimental and computational results reveal that variations in trap state density, carrier diffusion length, and exciton concentration modulate the size-dependent recombination coefficients k1, B, and C. Furthermore, the size-dependent carrier lifetime, trap state density, carrier density, carrier diffusion length, absolute PLQY, and cutoff wavelength are evaluated. Subwavelength-scale CsPbBr3 achieves lasing emission through synergistic mechanisms of carrier localization, low scattering loss, low defect state density, and high optical gain. This work establishes a foundational framework for designing size-tunable perovskite lasers and advances the understanding of scale-dependent photophysics in semiconductor gain media.