Greatly enhanced photocurrent in inorganic perovskite [KNbO₃]_0.9[BaNi_0.5Nb_0.5O_3-σ]_0.1 ferroelectric thin-film solar cell

Inorganic perovskite [KNbO₃]_0.9[BaNi_0.5Nb_0.5O_3-σ]_0.1 (KBNNO) ferroelectric thin films with narrow band gap (1.83 eV) and high room-temperature remnant polarization (Pr = 0.54 μC/cm²) was grown successfully on the Pt(111)/Ti/SiO₂/Si(100) substrates by pulsed laser deposition. Ferroelectric solar cells with a basic structure of ITO/KBNNO/Pt were further prepared based on these thin films, which exhibited obvious external-poling dependent photovoltaic effects. When the devices were negatively poled, the short-circuit current and open-circuit voltage were both significantly higher than those of the devices poled positively. This is attributed to enhanced charge separation under the depolarization field induced by the negative poling, which is superimposed with the built-in field induced by the Schottky barriers at the interfaces between KBNNO and the two electrodes. When a poling voltage of -1 V was applied, the device showed a short-circuit current as high as 27.3 μA/cm², which was by two orders of magnitude larger than that of the KBNNO thick-film (20 μm) devices reported previously. This work may inspire further exploration for lead-free inorganic perovskite ferroelectric photovoltaic devices.