Lanthanum and strontium modified bismuth ferrite based perovskites with ultra-narrow band gaps

Abstract The wide optical band gaps of ferroelectric perovskite oxides have restricted their light absorbing capacities in the photovoltaic devices. In this work, an ultra-narrow band gap E g and wide optical absorption across the ultraviolet-visible-infrared sunlight spectrum was achieved in lanthanum and strontium atoms modified Bi(Fe, Mn)O 3 perovskites by chemical substitution and defect engineering. XRD results show that the A and B site co-substituted samples are single phase. The XPS characterizations indicate the Fe ions are in the trivalent state for all the samples. The LM6 and SM6 samples exhibit an ultra-narrow band gap about 1.26 eV and 1.06 eV, respectively. The reduced E g was due to the defect states produced within the band gap, acting as a scaffold to give electrons to Fe 3d states and receive the electrons from O 2p states. Based on this research, these chemically modified BFO based perovskite could potentially extend its sunlight absorption deep into the infrared region.