  Outstanding optoelectronic properties and a facile synthesis render halide
perovskite nanocrystals (NCs) a promising material for nanostructure-based
devices. However, the commercialization is hindered mainly by the lack of NC
stability under ambient conditions and inefficient charge carrier injection.
Here, we investigate solutions to both problems, employing methylammonium lead
bromide (MAPbBr_3) NCs encapsulated in diblock copolymer core-shell micelles of
tunable size. We confirm that the shell does not prohibit energy transfer, as
FRET efficiencies between these NCs and 2D CsPbBr_3 nanoplatelets (NPLs) reach
73.6%. This value strongly correlates to the micelle size, with thicker shells
displaying significantly reduced FRET efficiencies. Those high efficiencies
come with a price, as the thinnest shells protect the encapsulated NCs less
from environmentally induced degradation. Finding the sweet spot between
efficiency and protection could lead to the realization of tailored energy
funnels with enhanced carrier densities for high-power perovskite NC-based
optoelectronic applications.
