  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.
