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Transient optical response in perovskite quantum dots (QDs) has remained elusive until now, which hinders their full utilization in optoelectronics. Herein, we reveal that the bandgap renormalization (BGR) dictates the main spectral and dynamical features of transient response in CsPbBr3 QDs. By monitoring the absorption spectral evolution of the monodispersed QDs, the representative BGR is explicitly observed, giving rise to the photoinduced absorption at the higher energy side of the lowest exciton peak in transient absorption spectroscopy. The BGR gradually increases upon photoexcitation as a result of the carrier distribution dependent screening effect. We further demonstrate that the BGR arises from both Coulomb screening and phonon heating under high pump intensities in CsPbBr3 QDs. The synergistic effect leads to the giant BGR energy (ΔE > 60 meV) and the unconventional relationship of ΔE ∝ n1/2, where n is the carrier density. These findings are important for the fundamental understanding and potential applications of the emerging halide perovskite semiconductors. [ABSTRACT FROM AUTHOR]

Developing mass-productive and high-performance microlaser particles (MLPs) by cost-effective approaches is highly promising for MLP-based optoelectronic applications, which remains a daunting challenge. Herein, we develop a novel solution-phase technique to realize the halide perovskite-based MLPs in a scalable manner. By regulating the dynamic process of crystallization in a two-step spin-coating procedure, the large-scale CsPbBr3 microcrystals are acquired. Importantly, the solution-processed CsPbBr3 microcrystals exhibit much stronger emission than the ones prepared by the chemical vapor deposition method, which is attributed to the low carrier trap density by the formation of a self-passivated and bromine-rich surface. These CsPbBr3 microcrystals with inverted pyramid morphology are demonstrated to support the whispering-gallery mode lasing, featuring low pump threshold and high Q-factor. Moreover, the technologically important single-mode lasing is achieved from the sub-5 μm-sized MLPs, thanks to the superior optical property. Eventually, the laser-emission-based gas sensor is demonstrated. These results represent a significant step toward scalable MLPs and related applications. [ABSTRACT FROM AUTHOR]

The electric field effect on the optical properties of semiconductors is important in terms of both fundamental physics and technological applications. Here, we explored the optical behavior of cesium halide perovskites under a varied electric field (F). We revealed the intrinsically distinct photoluminescence (PL) spectral evolution between the quantum-confined perovskites and the bulk phase, indicating the different carrier recombination behaviors under F. Strong PL quenching along with significant broadening of emission linewidths was observed. Notably, the CsPbBr3 colloidal quantum dots and nanoplatelets exhibit an unusual field-induced bandgap increase, which is attributed to the weakened orbital coupling between the Pb 6s and Br 4p states with the increase in F. These results could advance their application potential in optoelectronics. [ABSTRACT FROM AUTHOR]

Microlasers play an important role in the development of photonics and optoelectronics. As the rising star in the semiconductor family, all-inorganic lead halide perovskites (ILHPs) have been recognized as promising optical gain and lasing media. However, until now, achieving duplicable and single-mode microlasers remains a taunting challenge. Herein, we fabricated rectangular-shaped ILHP microsheets by the chemical vapor deposition method. The single-crystalline nature and the atomically smooth surfaces of the sample enable the achievement of lateral-cavity Fabry–Pérot (F-P) microlasers. Specifically, the lasing characteristics including the wavelength, mode spacing, and Q-factors can be well-reproduced along the axial direction of the individual microsheet. By regulating the width of the ILHP microsheet, the desirable single-longitudinal mode F-P microlaser was eventually achieved. Our results provide an enabling coherent light source for optics-related applications. [ABSTRACT FROM AUTHOR]