  High-entropy perovskite thin films, as the prototypical representative of the
high-entropy oxides with novel electrical and magnetic features, have recently
attracted great attention. Here, we reported the electronic structure and
charge transport properties of sol-gel-derived high-entropy
Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3 thin films annealed at various temperatures. By
means of X-ray photoelectron spectroscopy and absorption spectrum, it is found
that the conduction-band-minimum shifts downward and the valence-band-maximum
shifts upward with the increase of annealing temperature, leading to the
narrowed band gap. Electrical resistance measurements confirmed a
semiconductor-like behavior for all the thin films. Two charge transport
mechanisms, i.e., the thermally-activated transport mechanism at high
temperatures and the activation-less transport mechanism at low temperatures,
are identified by a self-consistent analysis method. These findings provide a
critical insight into the electronic band structure and charge transport
behavior of Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3, validating it as a compelling
high-entropy oxide material for future electronic/energy-related technologies.
