  Antimony sulfide (Sb2S3) and selenide (Sb2Se3) are emerging earth-abundant
absorbers for photovoltaic applications. Solar cell performance depends
strongly on charge carrier transport properties but these remain poorly
understood in Sb2X3. Here we report band-like transport in Sb2X3 by
investigating the electron-lattice interaction and theoretical limits of
carrier mobility using first-principles density functional theory and Boltzmann
transport calculations. We demonstrate that transport in Sb2X3 is governed by
large polarons with moderate Fr\"ohlich coupling constants (~ 2), large polaron
radii (extending over several unit cells) and high carrier mobility (an
isotropic average of > 10 for both electrons and holes). The room temperature
mobility is intrinsically limited by scattering from polar phonon modes and is
further reduced in highly defective samples. Our study confirms that the
performance of the Sb2X3 solar cells is not limited by intrinsic self-trapping.
