  The understanding of depletion layers is of major importance to control the
optical and electronic properties of metal oxide (MO) nanocrystals (NCs). Here,
we show that depletion layer engineering is the main mechanism of photodoping
of MO NCs. We show that the introduction of different electronic interfaces
induces a double-bending of the electronic bands and a distinct carrier density
profile. We found that the light-induced depletion layer modulation and bending
of the bands close to the surface of the nanocrystal is the main mechanism
responsible for the storage of extra electrons after photodoping in MO NCs. We
support our results by a combined experimental and theoretical approach in the
case of Sn:In2O3/In2O3 core-shell NCs, in which we compare numerical
simulations with empirical modeling and experiments. This allows not only to
extract the main mechanism of photodoping in MO NCs but also to engineer the
charge storage capability of MO NCs after photodoping. Our results are
transferable to other core-multishell systems, opening up a novel direction to
control the optoelectronic properties of nanoscale MOs by designing their
energetic band profiles through depletion layer engineering.
