  We report on the optical properties of CsPbBr3 polycrystalline thin film on a
single grain level. A sample comprised of isolated nanocrystals (NCs) mimicking
the properties of the polycrystalline thin film grains that can be individually
probed by photoluminescence spectroscopy was prepared. These NCs were analyzed
using correlative microscopy allowing the examination of structural, chemical,
and optical properties from identical sites. Our results show that the
stoichiometry of the CsPbBr3 NCs is uniform and independent of the NCs'
morphology. The photoluminescence (PL) peak emission wavelength is slightly
dependent on the dimensions of NCs, with the blue shift up to 9 nm for the
smallest analyzed NCs. The magnitude of the blueshift is smaller than the
emission linewidth, thus detectable only by high-resolution PL mapping. By
comparing the emission wavelengths obtained from the experiment and a rigorous
effective mass model we can fully attribute the observed variations to the
size-dependent quantum confinement effect.
