Ferroelectric photovoltaic response to structural transformations in doped BiFeO3 derivative thin films

Abstract

We report an investigation on crystallographic texturing, optical bandgap modulation and ferroelectric photovoltaic (FE-PV) response of semitransparent Au/BiFeO3 derivatives/Sn:In2O3 (ITO) thin film capacitors. Optimized A/B-site doping of respective Ce3+ and Mn2+ drives large-amplitude structural changes in BiFeO3 (BFO) films with partial tetragonal transformation and upsurge in extent of texture of (110) preferred orientation. Spin coated BFO, doped BiFe0.9Mn0.1O3, Bi0.88Ce0.12FeO3 and codoped Bi0.88Ce0.12Fe0.9Mn0.1O3 films of 350nm thickness on ITO coated corning glass exhibited optical transmittance of 65–80% in visible light range and revealed blue shift in optical band gap from 2.53 to 2.81eV due to splitting of t2g and eg orbital. Influence of single and co-doping on FE-PV response demonstrated crystallographic orientation and depolarizing field dependent behavior of short circuit current (JSC) and open circuit voltage (VOC). Current-voltage (J-V) characteristics of semitransparent Au/Bi0.88Ce0.12Fe0.9Mn0.1O3/ITO capacitors possessed large JON/JOFF ratio of approx. 104 at zero bias. Temporal dependence of photocurrent showed highly repeatable and stable response for consecutive ON/OFF cycles of illumination under solid state violet laser (405nm) of 160mW/cm2 intensity, a forward step towards non-destructive memory combining electronic and optical functionalities.