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

Highlights: • Structural modification induced ferroelectric-photovoltaic properties of pure and doped BiFeO₃ derivative films are studied. • Increase in polarization in turn photovoltaic response is observed with amplified texture of preferred (110) orientation. • Bi_0.88Ce_0.12Fe_0.9Mn_0.1O₃ thin film with optimum dopant amount showed better performance with J_ON/J_OFF ratio ~ 10⁴. • Octahedral tilting and splitting of t_2g and e_g levels induce continuous blue shift in direct band gap from 2.52 to 2.81 eV. • Optimized cation doping is effective methodology for enhanced ferroelectric photovoltaics towards opto-electronic devices. 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 BiFe_0.9Mn_0.1O₃, Bi_0.88Ce_0.12FeO₃ and codoped Bi_0.88Ce_0.12Fe_0.9Mn_0.1O₃ films of 350 nm 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 2.81 eV due to splitting of t_2g and e_g orbital. Influence of single and co-doping on FE-PV response demonstrated crystallographic orientation and depolarizing field dependent behavior of short circuit current (J_SC) and open circuit voltage (V_OC). Current-voltage (J-V) characteristics of semitransparent Au/Bi_0.88Ce_0.12Fe_0.9Mn_0.1O₃/ITO capacitors possessed large J_ON/J_OFF 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 (405 nm) of 160 mW/cm² intensity, a forward step towards non-destructive memory combining electronic and optical functionalities.