Event Details

Photoconductivity and photovoltaic studies on Bi1-xCaxFe1-yTiyO3 ceramics and thin films”

  • 2019-06-07
  • Mr. Subhajit Nandy

BiFeO3, a bandgap tunable (1.5 to 2.5 eV) multiferroic material, is capturing attention due to its favorable photovoltaic and photoferroelectric application. The advantage of using ferroelectric oxide in photovoltaic devices is it generates large photovoltage greater than the bandgap value. However, the major hindrance of ferroelectric oxide material is its poor efficiency (h<<1%) limited mainly by the low photocurrent density (<< µA/cm2) for photovoltaic applications. Hence, the motivation of this work involves understanding and improving the photocurrent response of BiFeO3based material. This is achieved either by creating oxygen vacancy (OV) in the lattice or by increasing surface OV defects at the grain boundaries. Measuring photoconductivity is a way to check the photosensitivity of a material. Several case studies carried out in this study include BiFeO3 nanoparticle and Bi1-xCaxFe1-yTiyO3 (x and y= 0, 0.1) ceramics and thin films. Aliovalent cation Ca2+ substitution at Bi3+ site in BiFeO3creates OV defects in bulk. Both bulk and surface OV defects at nano-sized grains enhance the photoconductivity by four orders in Bi1-xCaxFeO3-d ceramics. OV defects which form discrete energy defect states in the bandgap region just below the conduction band, thus significantly improve the photoconductivity. These defect states provide extra channel for photo excited electrons to flow through the grain boundaries. Similar enhancement in photoconductivity is observed in Bi1-xCaxFe1-yTiyO3 ceramic due to the dominant role of surface OV defects. Making use of this concept we have tested the photoconductivity and photovoltaic properties of thin films, grown on glass/FTO substrate by simple chemical solution method. The control on the short circuit current and open-circuit voltage are demonstrated.