Optically controlled polarization, photovoltaic and switchable diode behavior in multifunctional KBiFe2O5 composite film

This paper presents a light-induced diode effect in connection with the polarization direction and enhanced remanent polarization in polymer composite of the well-known multiferroic KBiFe2O5 film. Composite films of KBiFe2O5 with different PVA ratios were prepared by spin coating of ceramic slurry and the best composition with PVA was selected on the basis of its suitability for visible light absorption. KBiFe2O5-PVA composite film showed enhanced photovoltaic response under visible-light exposure with open circuit voltage of 2.11 V, photocurrent density of -8.3 x 10(-5) A/cm(2) and efficiency of 0.076%. The observed diode-like behavior in the composite film switched its direction with the flipping of electric polarization by an external voltage. The enhanced ferroelectric properties in the film were due to the reduction in leakage owing to the presence of nonconductive polymer in it. The composite film exhibited a piezoelectric coefficient of 1.98 nm/V and 2.2 nm/V corresponding to 15 V and -15 V respectively.