Superior ferroelectric photovoltaic properties in Fe -modified (Pb,La) (Zr,Ti)O3 thin film by improving the remnant polarization and reducing the band gap

Abstract

In order to develop ferroelectric photovoltaic devices with high power conversion efficiency, ferroelectric materials must have simultaneously large remnant polarization and narrow band gap so as to efficiently separate photo-generated carriers and absorb more sunlight. Based on this idea, in this report, we introduce Fe3+ into Pb0·93La0·07(Zr0·6Ti0.4)0.9825O3 ferroelectric thin film to increase the remnant polarization and decrease the band gap of the thin film. In doing so, we prepare Fe3+ doping Pb0·93La0·07(Zr0·6Ti0.4)0.9825O3 thin-film based photovoltaic devices. The experimental results indicate that with increasing the Fe3+ amount, the remnant polarization of the film first improves to the maximum value of 50 μC/cm2 at the 4.8 mol% Fe3+ content and then reduces gradually, while the band gap continuously decreases. In addition, at a negative poling voltage, the device exhibits larger short-circuit current and open-circuit voltage in comparison with those obtained at the positive poling voltage, which is attributed to the depolarization electric field originating from the remnant polarization of ferroelectric thin films in the same direction as the built-in electric field caused by the Schottky barrier. In this report, the most superior photovoltaic performances with the open-circuit voltage of as large as −0.55 V and short-circuit current of as high as 0.4 μA/cm2 are obtained in the device with 4.8 mol% Fe3+ amount and at −5 V poling voltage. This is on account of the improved sunlight absorbing properties and photo-generated carriers separation ability of the device. This work provides a novel idea for designing and preparing ferroelectric photovoltaic devices with high power conversion efficiency.