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

Fermi level pinning in doped metal oxide (MO) nanocrystals (NCs) results in the formation of depletion layers, which affect their optical and electronic properties, and ultimately their application in smart optoelectronics, photocatalysis, or energy storage. For a precise control over functionality, it is important to understand and control their electronic bands at the nanoscale. Here, we show that depletion layer engineering allows designing the energetic band profiles and predicting the optoelectronic properties of MO NCs. This is achieved by shell thickness tuning of core-shell Sn:In2O3-In2O3 NCs, resulting in multiple band bending and multi-modal plasmonic response. We identify the modification of the band profiles after the light-induced accumulation of extra electrons as the main mechanism of photodoping and enhance the charge storage capability up to hundreds of electrons per NC through depletion layer engineering. Our experimental results are supported by theoretical models and are transferable to other core-multishell systems as well.Surface states, and the combination of suitable materials, induce spatial gradients in the carrier density of doped metal oxide nanocrystals, affecting their electronic structure and plasmonic behavior. Here the authors demonstrate depletion layer engineering and control in ITO/In2O3 core-shell nanocrystals by tuning the shell thickness or by photodoping.