Efficiency Limit of Transition Metal Dichalcogenide Solar Cells

Transition metal dichalcogenides (TMDs) show great promise as absorber materials in high-specific-power (i.e. high-power-per-weight) solar cells, due to their high optical absorption, desirable band gaps, and self-passivated surfaces. However, the ultimate performance limits of TMD solar cells remain unknown today. Here, we establish the efficiency limits of multilayer MoS2, MoSe2, WS2, and WSe2 solar cells under AM 1.5 G illumination as a function of TMD film thickness and material quality. We use an extended version of the detailed balance method which includes Auger and defect-assisted Shockley-Reed-Hall recombination mechanisms in addition to radiative losses, calculated from measured optical absorption spectra. We demonstrate that single-junction solar cells with TMD films as thin as 50 nm could in practice achieve up to 25% power conversion efficiency with the currently available material quality, making them an excellent choice for high-specific-power photovoltaics.Comment: 24 page

Extended Hückel Theory for Quantum Transport in Magnetic Tunnel Junctions

Abstract-Spin-resolved conductivities in magnetic tunnel junctions are calculated using a semiempirical tight-binding model and non-equilibrium Green's functions. The performance of half-metallic electrodes is studied by comparing conventional Fe-MgO-Fe structures to Co2FeAl-MgO-Co2FeAl structures. The results show higher tunneling magnetoresistance and resistancearea product for Co2FeAl devices across a wide bias range