Polaron formation in Bi-deficient

is a charged ordered Peierls-like perovskite well known for its superconducting properties upon K or Pb doping. We present a study on the transport and electronic properties of perovskite with strong Bi deficiency. We show that it is possible to synthesize thin layers with Bi vacancies above 8-10% by depositing an yttrium-stabilized zirconia capping layer. By combining transport measurements with ab initio calculations we propose a scenario where the Bi vacancies give rise to the formation of polarons and suggest that the electrical transport is dominated by the migration of these polarons trapped at sites. Our paper shows that cation vacancies engineering, hardly explored to date, appears as a promising pathway to tune the electronic and functional properties of perovskites.