Funneling Light and Energy with New Materials

Dean Sigler Electric Aircraft Materials, Solar Power, Sustainable Aviation Leave a Comment

Dr. Adolfo De Sanctis, a Research Fellow in the Quantum Systems and Nanomaterials group at the University of Exeter (UK), earned his Ph. D. in physics with a dissertation on “Manipulating light in two-dimensional layered materials” (Nature Communications, May 2017).  The video below gives a short-hand view of his work.

Other, less scholarly outlets (like this one) give an easy-to-read view of what he has accomplished, and why his research is of interest for many applications – including energy harvesting.

Green Optimistic reports, “A team of researchers from the University of Exeter developed a solar cell with a record 60% efficiency. The idea behind this breakthrough is similar to using a ‘funnel’: corralling an amorphous collection of electrical charges into a more precise area, where they can be transferred into use. Using this idea, the researchers increased the efficiency of a solar cell from 20 to 60 percent.  The Exeter team sees their research as a ‘gateway’ for further research and development.”  That means any practical applications are more than the popular “five years away.”

Inverse charge funneling in strained HfS2.  Somewhere north of your editor’s pay grade, the Nature Communications article explains, ” The compression induces tensile strain away from the HfS2/HfO2 interface, resulting in the spatial modulation of the bandgap. b Ab initio calculations of the valence band maximum (VBM) and conduction band minimum (CBm) of 1T-HfS2 as a function of strain in the Γ → Γ (direct gap) and Γ → M (indirect gap) directions. c Change in bandgap as a function of strain in the two directions, with respect to the unstrained bandgap (relaxed lattice constant a0 = 3.625 Å). Inset: calculated band structure of 1T-HfS2″

Solar-powered cars, aircraft or boats could be smaller, without the need to add area for solar cells.  Airplanes could be more efficient and faster, or add range and endurance in their existing size.

De Sanctis’ team created a 2D material with a graphene base and added a new material – hafnium disulfide.  This enables the graphene/hafnium material to stretch and compress in ways that would rip ordinary materials apart.  The enhanced materials can sustain a 25-percent level of stress compared to a puny 0.4 percent for conventional materials.

Applying this to solar collectors, photoexcited charges can be funneled away from the excitation region and towards areas where they can be efficiently extracted.

The abstract for the team’s paper in the journal Nature Communications concludes on this hopeful note.  “These results open the route towards the exploitation of strain-engineered devices for high-efficiency energy harvesting and sensing applications, with the potential to overcome the intrinsic limitations of current solar cells by exploiting both hot-carriers extraction and lossless transport, to achieve efficiencies approaching the thermodynamic limit in photovoltaic devices. The use of atomically thin materials could open the door to the incorporation of such devices in emerging wearable electronics technologies and smart buildings, creating a new paradigm in energy harvesting.

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