Stable green-emitting perovskite nanocrystals (NCs) with general formula APbBr 3 , exhibiting a high photoluminescence quantum yield (PLQY), narrow bandwidth, and adjustable PL in the 510−535 nm region are coveted materials for optoelectronic applications. A generic method of obtaining both hybrid and all-inorganic perovskite NCs with the desired characteristics is, however, lacking. Herein, we report a methodology for the synthesis of CsPbBr 3 , FAPbBr 3 , and MAPbBr 3 NCs employing N-bromosuccinimide as the bromide precursor. The NCs show uniform size distribution, PL maxima between 512 and 531 nm, near-unity PLQY with a fwhm of 18−22 nm, and remarkable stability in ambient conditions, in the presence of water and under UV irradiation. Not only do these exceptional characteristics of the NCs indicate their high potential in real applications, but this new methodology may also open new vistas for direct synthesis of other perovskites with high PLQY and stability without resorting to any additional postsynthesis treatment.

Studies on ultrafast dynamics of various photo-induced processes in perovskite nanocrystals and their composites, and insights obtained from them are presented in this review.

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a Ph.D. student under Prof. Anunay Samanta. His research interest is the synthesis and understanding of ultrafast photoinduced processes of highly luminescent perovskite nanocrystals.Sumanta Paul, after completing his Master's degree from the School of Chemistry, University of Hyderabad, in 2017, is working on his Ph.D. under the supervision of Prof. Anunay Samanta. His research focuses on the synthesis and study of photophysical properties of perovskite nanocrystals at the bulk and single-particle levels.

Despite their low band gap, the utility of CsPbI 3 nanocrystals (NCs) in solar photovoltaic and optoelectronic applications is rather limited because of their phase instability and photoluminescence (PL) intermittency. Herein we show that phase-pure, monodispersed, stable and highly luminescent CsPbI 3 NCs can be obtained by tweaking the conventional hot-injection method employing NH 4 I as an additional precursor. Single-particle studies show a significant suppression of PL blinking. Among all NCs studied, 60% exhibit only high-intensity ON states with a narrow distribution of intensity. The remaining 40% of NCs exhibit a much wider distribution of PL intensity with a significant contribution of low-intensity OFF states. Excellent characteristics of these CsPbI 3 NCs are shown to be the result of NH 4 + replacing some surface Cs + of an iodide-rich surface of the NCs. These phase-stable and highly luminescent CsPbI 3 NCs with significantly suppressed PL blinking can be useful single-photon emitters and promising materials for optoelectronic and solar photovoltaic applications.