An EPR investigation on reduced Sn centres in SrSnO3 perovskite

The use of the wide band gap SrSnO3 semiconductor in photocatalysis has grown over the last few years, driven predominantly by sustainability given that its constituents are all Earth abundant elements. Using EPR spectroscopy, we elucidate the paramagnetic species present in the material, either intrinsic or photo-generated. EPR measurements confirmed the presence of paramagnetic oxygen vacancies (g = 2.0058) and a defect sensitive to visible light irradiation despite a wide optical band gap of 4.1 eV. This defect was confirmed to be Sn3+ (g = 2.014 and g = 1.994). Its concentration appears to increase with visible light irradiation, suggesting a photo-induced formation associated with electronic transitions from Sn2+ intra-band gap states to the conduction band.