An amine-free method is used to systematically investigate the role of Cs, Pb and Br in hot-injection synthesis.

We demonstrate that Ag­(I) complex can fix bromide on the nanocrystal surface, reduce surface trap density, and as a result efficiently passivate the surface of CsPbBr3 nanocrystals. This passivation makes the photoluminescence (PL) intensity increase several times. The PL kinetics study clearly shows that the decay lifetime increased after the passivation. TEM and XPS analyses demonstrated the existence of Ag on the nanocrystal surface. In addition, we utilize single-particle spectroscopy combined with in situ light analysis to further confirm the PL enhancement effect. On the contrary, the passivation leads to the extraordinary photostability of CsPbBr3 nanocrystals, with 80% PL intensity retained after UV illumination for 5 days under ambient conditions.

In recent years, there has been an unprecedented rise in the research of halide perovskites because of their important optoelectronic applications, including photovoltaic cells, light-emitting diodes, photodetectors and lasers. The most pressing question concerns the stability of these materials. Here faster degradation and PL quenching are observed at higher iodine content for mixed-halide perovskite CsPb(BrI) nanocrystals, and a simple yet effective method is reported to significantly enhance their stability. After selective etching with acetone, surface iodine is partially etched away to form a bromine-rich surface passivation layer on mixed-halide perovskite nanocrystals. This passivation layer remarkably stabilizes the nanocrystals, making their PL intensity improved by almost three orders of magnitude. It is expected that a similar passivation layer can also be applied to various other kinds of perovskite materials with poor stability issues.

All-inorganic perovskite (CsPbX 3 , X = Cl, Br, I) nanorods (NRs) not only retain their inherent advantages such as a high photoluminescence quantum yield and broad wavelength tunability but also exhibit superior photophysical properties including their extremely strong multiphoton absorption (MPA). However, the spectral dynamics and MPA properties of CsPbX 3 NRs have not been fully investigated. Here, we report comprehensive comparison studies on the femtosecond spectral dynamical properties of CsPb(Br 0.8 Cl 0.2 ) 3 , CsPbBr 3 , and CsPb(Br 0.85 I 0.15 ) 3 NRs, including their influences on their hot-carrier cooling, biexciton lifetime, and biexciton binding energy. Interestingly, although the three kinds of perovskite NRs have similar diameters and lengths, they differ significantly in their nonlinear optical properties, among which the CsPb(Br 0.85 I 0.15 ) 3 displayed the greatest MPA cross sections. Furthermore, the multiphotonexcited stimulated emission of CsPb(Br 0.8 Cl 0.2 ) 3 and CsPbBr 3 NRs is demonstrated. This work indicates that CsPbX 3 (X = Cl, Br, I) NRs are excellent candidates for exploring their applications in different optoelectronic devices.

We have synthesized highly luminescent CsPbBr3 nanorods through an oriented-attachment mechanism assisted by the ligand-regulation at the water–oil interface.

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Recent microstructural studies on lead halide perovskite nanocrystals have consistently reported the coexistence of byproduct nanoparticles (NPs). However, the nature of these NPs and their formation mechanism are still a matter of debate. Herein, we have investigated the structure and compositions of the NPs located on colloidal cesium lead bromide nanocrystals (CsPbBr 3 NCs), mainly through aberration-corrected transmission electron microscopy and spectroscopy. Our results show that these NPs can be assigned to PbBr 2 and CsPb 2 Br 5 . The new CsPb 2 Br 5 species are formed by reacting CsPbBr 3 NCs with the remaining PbBr 2 during the drying process. In addition, observation of the metallic Pb NPs are ascribed to the electron damage effect on CsPbBr 3 NCs during transmission electron microscopy imaging.Keywords: lead halide perovskite materials; colloidal cesium lead halide nanocrystals; scanning transmission electron microscopy and spectroscopy