  We evaluate the tunneling short-circuit current density $J_{TU}$ in a
$p$-$i$-$n$ solar cell in which the transition metal dichalcogenide
heterostructure (MoS$_2$/WS$_2$ superlattice) is embedded in the intrinsic $i$
region. The effects of varying well and barrier widths, Fermi energy levels and
number of quantum wells in the $i$ region on $J_{TU}$ are examined. A similar
analysis is performed for the thermionic current $J_{TH}$ that arises due to
the escape and recapture of charge carriers between adjacent potential wells in
the $i$-region. The interplay between $J_{TU}$ and $J_{TH}$ in the temperature
range (300 K - 330 K) is examined. The thermionic current is seen to exceed the
tunneling current considerably at temperatures beyond 310 K, a desirable
attribute in heterostructure solar cells. This work demonstrates the
versatility of monolayer transition metal dichalcogenides when utilized as
fabrication materials for van der Waals heterostructure solar cells.

Materials Science