Effective threshold reduction in a CH3NH3PbBr3 perovskite random laser due to multireflection processes at the perovskite/PSS interface.

Despite many successful realizations of laser operations in various micro/nanostructured lead halide perovskites (LHPs), the electron–hole plasma (EHP) lasing dynamics has only rarely been reported, especially for wide-gap Cl-rich perovskites. In this work, the temporal lasing dynamics of whispering gallery mode (WGM) CsPbCl m Br3–m microplate lasers are systematically investigated, for the first time, with a streak camera system. As the pump fluence increases, the gain profile exhibits a monotonous redshift, indicating the EHP lasing in the microplate cavity, while an opposite shift of the gain region is observed with time decay due to the gradual depletion of carriers. This directly reflects the change of the bandgap renormalization effect at varying pump fluences. Additionally, the individual lasing modes present identifiable blueshifts with elevated pump levels and redshifts with time delay, which can be unraveled by the carrier-induced refractive index change in the LHP cavity. Moreover, the wavelength-dependent lasing duration demonstrates that lasing in the EHP regime depends not only on the carrier density, but also on the bandgap variation with carrier density. By directly modulating the pump fluence, the onset delay of the microlaser can be efficiently tuned. Our results provide a comprehensive understanding of the EHP lasing mechanism and carrier dynamics in the WGM LHP micro/nanolasers and will push their technological relevance in integrated photonics.

This is the first study of lead halide perovskites (LHPs) that compares the coupling strengths between longitudinal optical (LO) phonons and free or localized excitons. In this research, we measured the excitation density and temperature dependence of the photoluminescence (PL) spectra in the range of 4-300 K in a CsPbBr 3 single crystal. The PL peak energy of the free excitons monotonically blueshifts when the temperature increases, and so does the localized excitons until the temperature reaches 80 K. Above 80 K, however, the PL peak energy of the localized excitons redshifts when the temperature increases. We analyzed this unique temperature dependence using the configuration coordinate model, focusing on the exciton -LO phonon interaction. We showed that this unique temperature dependence can be exhibited as the localized excitons couple with the LO phonons with enhanced strength and have larger relaxation energy than the free excitons.

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