Narrowing the Band Gap of Nanosized Fe-Doped Bismuth Titanate via Mechanically Induced Oxygen Vacancies

Abstract

The band gap is an essential parameter to estimate the absorption of radiation in photovoltaic cells. However, the wide band gap of complex oxides limits their application in optoelectronic devices, even though they have many excellent properties. The aim of this research is to narrow the band gap of a series of Fe-doped lanthanum-modified bismuth titanate (Fe-BLT) powders by tuning the particle size via high-energy ball milling. Subsequently, smaller size particles were collected by centrifugal separation, which were then examined by scanning electron microscopy (SEM) and ultravioletvisible spectroscopy (UV-Vis). The X-ray diffraction (XRD) results indicate that the decrease in size did not affect the orthorhombic symmetry. Remarkably, the optical band gap of nanosized particles significantly declined in comparison with that of microsized particles according to the UVVis results, and this observation was attributed to the formation of oxygen vacancies. Based on our observations, the photovoltaic efficiency of these promising complex oxide materials could feasibly be enhanced, which would maximize their performance in optoelectronic devices.