Photovoltaic effect of lead-free (Na0.82K0.18)0.5Bi4.5Ti4O15 ferroelectric thin film using Pt and indium tin oxide top electrodes

We have grown a Bi-layer structure (Na0.82K0.18)0.5Bi4.5Ti4O15 (NKBiT) ferroelectric thin film on Pt(111)/TiO2/SiO2/Si(100) substrate by using the chemical solution deposition method and deposited two kinds of thin Pt and indium tin oxide (ITO) top electrodes. The photovoltaic behaviors of Pt/NKBiT/Pt and ITO/NKBit/Pt capacitors were investigated over the wavelength range of 300–500 nm. When NKBiT thin film is illuminated by the corresponding wavelength of the film's energy band gap (Eg), a photocurrent is generated due to the Schottky barrier between electrode and film, and an internal electric field is originated by the depolarization field. The maximum photocurrent density and power conversion efficiency of the ITO/NKBiT/Pt capacitor in the poled-up state are obtained as 45.75 nA/cm2 and 0.035%, respectively, at 352 nm. The photocurrent density and power conversion efficiency of the ITO/NKBiT/Pt capacitor increased to 3.5 times higher than that of the Pt/NKBiT/Pt capacitor.