P-type conductive BaZrS3 thin film and its band gap tunning via Ruddlesden-Popper Ba3Zr2S7 and titanium alloying

BaZrS3 is an emerging chalcogenide perovskite that possesses excellent light absorption and carrier transport abilities comparable with the halide perovskites. Besides, it shows better stability and lower toxicity. However, BaZrS3 is only reported as n-type conductivity in previous studies. Lack of p-type conductivity limits its appli-cation into solar cells or other complex devices. In addition, strategies to tailor its band gap (-1.8-2.2 eV) to optimal range (-1.4-1.5 eV) for solar absorbers are not well established. In this work, for the first time, we demonstrate p-type conductive BaZrS3 thin film with the hole concentration and mobility as high as-1018 cm-3 and 30 cm2/Vs, respectively, and the Ba vacancy was the most probable defect contributing to the p-type con-ductivity. Ruddlesden-Popper Ba3Zr2S7 thin film and orthorhombic BaZr1-xTixS3 alloy thin film are also prepared by co-sputtering from BaZrS3 and BaS/BaTiS3 targets. Inspiringly, 4% Ti substitution for Zr can tune the band gap of BaZr1-xTixS3 from 2.2 to 1.5 eV, a near ideal value for photovoltaic absorbers according to Shockley -Queisser limit. Successful optoelectronic tuning strategies for chalcogenide perovskite in this work may pave the way for its application into complex optoelectronic devices like solar cells.