Bandgap engineering of cobalt-doped bismuth ferrite nanoparticles for photovoltaic applications

摘要

Thebandgap energy range of multiferroic bismuth ferrite is 2.2-2.7 eV, making it a promising candidate for photovoltaic (PV) applications. But its efficiency is still very low (<2%). This report thus focusses on the application of bismuth ferrite (BFO) engineered with cobalt (Co) doping and on the tuning of its bandgap energy (Eg). BiFeO3 is a unique multiferroic material that simultaneously displays both ferromagnetic and ferroelectric properties at room temperature. Co doped with pure BiFeO3 (BiFe(1-x)CoxO3; x=0,0.05, 0.1 and 0.15) was synthesized by the sol-gel method and annealed at 600 degrees C. X-ray diffraction shows the well-arranged crystalline structure and peaks of pure and doped-BiFeO3 nanoparticles. A suitable reduction of Eg has been observed for Co-doped BiFeO3, which may be appropriate for the effective use in PV solar cells. Thermogravimetric analysis and differential scanning calorimetry were used to investigate the thermal decomposition character of the xerogel powder and the pattern of pure and doped BiFeO3 phases. Field emission scanning electron microscopy images show the surface crystallography of pure and Co-doped BiFeO3. Co-doped BiFeO3 has considerably reduced the crystallite and particle size of the samples. We have calculated the Eg of pure and doped BiFeO3 using a UV-Vis-NIR spectrophotometer and the results show the important reduction of Eg (1.60 eV) of the Co-doped samples, which may have potential applications in PV solar cells.