The motivation for the present work is a 2016 publication by Kim et al, entitled "Thermally stable p-n-junctions based on a single transparent perovskite semiconductor BaSnO 3 ", where K-doped (p-type) and La-doped (n-type) BaSnO 3 were deposited via pulsed laser deposition (PLD) to fabricate a transparent p-n junction. Perovskite BaSnO 3 is well characterised as a TCM, with an optical gap of around 3.6 eV, conductivity up to 5000 S cm -1 when doped with La, and single crystal electron mobility up to 320 cm 2 V -1 s -1 , which is the record for any transparent material. Its defect chemistry has been studied previously with hybrid density functional theory (DFT), indicating weak n-type semiconducting behaviour when undoped, and degenerate conductivity when doped with La or F. However, computational investigation into its p-type defect chemistry have thus far been overlooked.