Control of electronic band profiles through depletion layer engineering in core-shell nanocrystals

TL;DR

This paper demonstrates that depletion layer engineering in core-shell nanocrystals controls their electronic band profiles and charge storage capabilities, combining experimental and theoretical methods to reveal mechanisms of photodoping in metal oxide nanocrystals.

Contribution

It introduces a novel approach to control optoelectronic properties of metal oxide nanocrystals by designing their band profiles through depletion layer engineering.

Findings

Depletion layer modulation is key to photodoping in MO nanocrystals.

Electronic interface design induces band bending and carrier density profiles.

Experimental and theoretical analysis confirms the main mechanism of charge storage.

Abstract

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.