  Transition metal dichalcogenides (TMDCs) have garnered significant interest
in optoelectronics, owing to their scalability and thickness-dependent
electrical and optical properties. In particular, thin films of TMDCs could be
used in photovoltaic devices. In this work, we employ $ab$ $initio$ many-body
perturbation theory within $G_0W_0$-BSE approach to accurately compute the
optoelectronic properties of thin films of 2H-TMDCs composed of Mo, W, S, and
Se. Subsequently, we evaluate their photovoltaic performance including exciton
recombination effects, and show this is a key ingredient. We obtain
efficiencies of up to 29\% for a 200-nm thick film of \ce{WSe2}, thus providing
an upper limit. We also include other \textcolor{black}{phenomenological}
recombination mechanisms that could be present in current samples. This
slightly reduces efficiencies, indicating that even with current synthesis
technologies, there is still potential for further enhancement of TMDCs'
performance in photovoltaic applications.
