Within MOPTOPus we have developed a novel solid-state nanoscale material system displaying light-driven capacitive charging dynamics. This system is capable of both harvesting optical energy and quasi-permanently storing it, thus demonstrating a new paradigm of nanoscale energy systems for autonomous miniature energy storage. The novel system is composed of a 2D material overlaid with a monolayer of doped indium tin oxide nanocrystals. By achieving direct coupling between the nanocrystals and the 2D semiconductor for the first time, we have discovered a method to quasi-permanently change the charge states of the two components: upon UV illuminationphotodoping, photo-generated holes in the nanocrystal efficiently transfer to the 2D semiconductor forming a nanoscale, capacitor-like hybrid structure that remains charged even after the UV illumination is terminated, for more than 72 days (we have only measured up to 72 days so far). This phenomenon, which is altogether distinct from transient charge transfer effects that diminish on ultrafast timescales, opens up new routes for micro/nanoscopic solid-state elements that generate and store energy via remote and local, all-optical charging. The temporal variation of the charge density in this 0D-2D hybrid system lead us to evaluate the observed charging dynamics with a capacitor model. Our estimates indicate that energy storage at levels of ~1 μJ cm-2 are possible in this system that has an overall thickness of only ~12 nm. Based on our current findings, we predict that even better performance can be achieved through, for instance, strain engineering or vertical heterostructure engineering of the 2D material, opening up an entirely new parameter space for follow-up works and catalyzing the development of a fully light-driven nanocapacitor system as a new form of autonomous energy storage. Moreover, we see the potential of this hybrid system to locally inject carriers on the micrometer scale as a step towards contactless light-driven nanoelectronics. The findings of this work reveal a new foundational building block for next-generation nanodevices that can enable remote-control of local charge density, novel light-driven energy storage schemes, and light-activated nanocircuitry. . (1,2)
(1) Kriegel, I. et al. J. Phys. Chem. C 2020, 124 (14), 8000–8007.
(2) Kriegel, I. et al. Arxiv 2018, 1810.05385.
