We have studied the optical and structural properties of CsPbBr 3 perovskite nanocrystals (NCs) fabricated with various reaction times. The temporal evolution of the ensemble optical properties, such as absorption and fluorescence (FL) spectra and photoluminescence quantum yield (PLQY), was recorded under a set reaction temperature (170 ∘ C) and various amounts of time (5 s -60 min). The FL intensity of the CsPbBr 3 NCs gradually decreased with increasing reaction time, and the observed PLQY of

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... the CsPbBr 3 NCs ranged from less than 20% up to 35% because of the enlarged crystal size and the induced charge trap states. The FL peaks of as-obtained CsPbBr 3 NCs were tuned in the range of 516.8 to 526.8 nm with increasing reaction time as a result of the ripening phenomenon. Transmission electron microscopy and selected area electron diffraction analysis were performed to analyze the structural properties. The results revealed that the average edge length of CsPbBr 3 NCs with a reaction time of 5 s was 13.4 nm and confirmed that the cubic crystal structure was well ordered.