Two Dimensional Materials for Photonic Devices

ended

The need for inexpensive yet highly efficient photodetectors and solar cells is driving the search for a new generation of semiconductors that have high absorbance in the visible, broad wavelength operation range, are transparent and flexible albeit with strong light-matter interaction, and are easy to process. Manufacturing these optoelectronic devices at a large scale involves concerns at technological, economical, ecological, social and political levels. Ideally, the new materials are abundant, easily processed and feature long term stability and non-toxicity. The advent of 2D transition metal dichalcogenides (TMDCs). e.g., MoS2 and WS2, has generated great expectations since these materials fulfill all these requirements. 2D-TMDCs exhibit direct band gaps, high absorption coefficients, and high carrier mobility values, making them promising candidates for optoelectronic applications. The out-of-plane quantum confinement responsible for the direct bandgap in the monolayer, also allows for the modulation of the bandgap as a function of the number of layers. However, for photovoltaics (PV), even if transparency is an important attribute in some niche markets, e.g. building-integrated PV, thickness-limited absorption poses a challenge in general. To overcome this issue, we propose a photonic nanostructuration to maximize light harvesting in these devices. We will combine strong interference effects based in the small penetration in a metallic substrate and the light trapping due to the nanostructuration by lithography of TMDCs over a metallic substrate. Resonators with high-quality factors will have potential applications in light harvesting devices, such as photodetectors, but also in solar cells. We will design and fabricate such an efficient photodetector, and also a solar cell incorporating the photonic design, and demonstrate enhanced performance in a metal back reflector/TMDC/graphene device.