LAUSR

Abstract [KNbO 3 ] 0.9 [BaNi 1/2 Nb 1/2 O 3 ] 0.1 (KBNNO) perovskite ferroelectric thin films with narrow band gap (up to 1.39 eV) and good ferroelectric properties are prepared successfully by pulsed laser deposition. The emergence of Ni 3 d gap states is confirmed to be responsible for the narrowing down of band gap of KBNNO, which correlates almost linearly with the increase of Ni content. Via a linear fit, a quantitative relationship between the Ni content and the band gap is established, laying a foundation for future design of new KBNNO-based materials with narrow band gap. The room-temperature remnant polarization (up to 1.4 μC/cm 2 ) of the KBNNO thin film is by an order of magnitude higher than that (0.1 μC/cm 2 ) of previously reported thick film with 20 μm thickness. Both narrow band gap and large room-temperature remnant polarization make KBNNO thin films very attractive for developing ferroelectric photovoltaic devices with high conversion efficiencies.