Elastic Strain Engineering for Unprecedented Materials Properties

J. Li
Massachusetts Institute of Technology, US

Keywords: modeling and simulation, phtovoltaic, eleastic strain

Summary:

An optoelectronic material with a tunable, spatially varying bandgap is highly desirable for photovoltaics, photocatalysis and photodetection. Elastic strain has the potential to be used to achieve rapid and reversible tuning of the bandgap. However, as a result of plasticity or fracture, conventional materials cannot sustain a high enough elastic strain to create sufficient changes in their physical properties. Recently, an emergent class of materials named ‘ultrastrength materials’ [Prog. Mater. Sci. 55 (2010) 710] have been shown to avoid inelastic relaxation up to a significant fraction of their ideal strength. Here, we illustrate theoretically and computationally that elastic strain is a viable agent for creating a continuously varying bandgap profile [Nature Photonics 6 (2012) 866; MRS Bulletin February 2014 special issue] in an initially homogeneous, atomically thin membrane. We propose that a photovoltaic device made from a strain-engineered MoS2 monolayer will capture a broad range of the solar spectrum and concentrate excitons or charge carriers. By controlling the elastic strain field statically or dynamically, one opens up a much larger parameter space for optimizing the functional properties of materials, which gives a new meaning to Feynman’s 1959 statement “there's plenty of room at the bottom”.